I checked out a great collection of essays called _A Companion to Phenomenology and Existentialism_. I want to get a few notes down here for later use. The chapter on affectivity is by B. Han-Pile.
As an ontologist, Heidegger was interested in uncovering the deepest role played by affectivity in world disclosure. There are two tasks. First it's important to differentiate between mood and psychological 'feelings.' Second, it's important to focus on how moods work.
Heidegger wants to tell us about Dasein in BT. He says that there's three structures, existentials, that are conditions for the possibility of being-in-the-world the way Dasein is. The three are Befindlichkeit, Verstand, and Rede; that is, affectivity, understanding, and discourse.
In terms of affectivity, you need to realize that affectivity is the capacity of being receptive to moods. Affectivity, in that way, is like resonance. When affectivity is realized you receive an attunement or mood. There's three things specific to moods. 1) They indicate our throwness. 2) They "disclose being-in-the-world as a whole" (BT, p. 136). 3) They are the modality by which things matter to us. This means they are "the particular mode in which something exists or is experienced or expressed" (Google define: modality).
Mood and thrownness
We are thrown over and into moods. There is passivity and groundlessness inherent to our being. Therefore, "moods indicate 'a disclosive submission to the world' (BT, p. 137-8)" (Han-Pile, p. 245). Moods are interstitial. "[P]ublicness, as the kind of being which belongs to the 'One', not only has in general its own way of having a mood, but needs moods and 'makes' them for itself" (p. 139).
Mood and being-in-the-world
Moods modulate but having a mood is a constancy. We often aren't aware explicitly of our mood. Moods are "prior to all cognition and volition, and beyond their range of disclosure" (BT, p. 136). "Moods are the very background on which both world and Dasein are disclosed, and from which only mental directedness toward objects is possible (Han-Pile, p. 245).
Mood and modality
Moods are the modality by which things matter to us. This means they are "the particular mode in which something exists or is experienced or expressed" (Google define: modality). The entities somebody encounters do not have subjective qualities projected upon them by somebody. "On the contrary, we can only be affected by entities, and thus react to them or make decisions regarding them, if they have already been disclosed to us ... by the mood we are in" (Han-Pile, . 246). Something "can ultimately be boring only because the attunement already plays around it. It does not cause the boredom, nor does it receive it merely as something attributed by the subject. In short: boredom - and thus ultimately every attunement - is a hybrid, partly objective, partly subjective" (Heidegger, 2001, p. 88; quoted in Han-Pile, p. 246).
Gendlin and affectivity
Eugene Gendlin relied on Befindlichkeit to develop his focus approach to experiential psychology. He outlined his understanding in the following citation given for future reference: Gendlin, E.T. (1978) ‘Befindlichkeit: Heidegger and the Philosophy of Psychology’,
Review of Existential Psychology and Psychiatry 16(1–3): 43–71.
Gendlin translated Befindlichkeit as the "human feeling capacity" (p. 1, my pagination). He clarifies four distinctions about "feelings, affects, and moods as Befindlichkeit" (p. 3). First, this notion of mood refers to "how we sense ourselves in situations" (p. 3). It is as if we are placing ourselves outside ourselves and then gathering a sense of how we are getting along in the world. Moods are interstitial rather than interactiontional because being interactional "assumes that first there are two, and only then is there a relation between them. For Heidegger, humans are their living in the world with others. Humans are livings-in, and livings-with" (p. 3). "A feeling must be thought of both as sensed and as in the world" (p. 13).
Second, moods pervade our being-in-the-world even if we are not acutely in acknowledgement of mood. "It is no merely internal state or reaction, no mere coloring or accompaniment to what is happening. We have lived and acted in certain ways for certain purposes and strivings and all this is going well or badly, but certainly it is going in some intricate way. How we are faring in these intricacies is in our mood....We have had some part in getting ourselves into these situations, in making the efforts in response to which these are now the facts, the difficulties, the possibilities, and the mood has the implicit 'understanding' of all that because this understanding was inherent already in how we lived all that, in an active way" (pp. 3-4). "A feeling must be thought of as containing its own understanding of how one is living" (p. 13).
Third, the understanding of mood is implicit and not cognitive. Moods are sensed rather than thought. The sensation may be indirectly acquired or otherwise unnoticed. There are no units of mood. Moods have "implicit complexity" (p. 4). The understanding and meaning of mood is implicit in that a) it might not even be known; b) it's never atomized in units; and c) holistically complex. Fourth, discourse (Rede), talk, or saying is shot through with mood. "We sense ourselves living in situations with others, with an implicit understanding of what we are doing and with communication between us always already involved" (pp. 4-5). Even though mood is primarily sensed, "the feeling-understanding" has the power to guide speech" (p. 14). From the four distinctions we can surmise that the concept of Befindlichkeit "eliminates the distinction between inside and outside, as well as between self and others" (p. 7).
Gendlin offers many quotes from Being and Time to support the connection between moods (composure) and understanding. "Mood discloses in the manner of turning toward, or turning away from one's own Dasein. The bringing before the 'that it is' ... may be authentically revealing or inauthentically covering up" (Heidegger, 1962, p. 340). "Authenticity is fundamentally grounded in Befindlichkeit and its understanding, and requires bringing oneself before how one is disclosed in the mood" (Gendlin, 1978, p. 20).
Gendlin has more to say about understanding. "Understanding sketches out possibilities, or one can say (even in English) it 'throws out' possibilities, as one throws out suggestions" (p. 21). "The mood is the possibilities we already are, as being thrown into them" (p. 24). The mood is the stance we take in the moment. In the way of having a mood Dasein 'sees' possibilities from out of which it is. In the sketching disclosing of such possibilities it is always already in a mood (Heidegger, 1962, p. 148).
"Befindlichkeit is a basic existential way in which Dasein (being-here) is its here. It not only characterizes Dasein ontologically, but because of its disclosing, it is at the same time of basic methodological significance for the existential analytic. Like any ontological interpretation whatsoever, this analytic can only, so to speak, 'listen in' to the previously disclosed being of something that is.... Phenomenological interpretation must give Dasein the possibility of original disclosing, to raise the phenomenal content of this disclosing into concepts" (Heidegger, 1962, pp. 139-140). Gendlin then claims that this is explicitly saying "that Befindlichkeit is the disclosing on which phenomenological method depends....If the disclosing of Befindlichkeit isn't there as part of the method, it will be free-floating, and not phenomenological" (p. 29).