First, my understanding of class struggle qua negativity is classical, in the sense of finding its origin in an experience of commodification and alienation that bears, primarily, on time. In Marx's classic statement from part 7, in the chapter on 'The General Law of Capitalist Accumulation':
within the capitalist system all methods for raising the social productiveness of labour are brought about at the cost of the individual labourer; all means for the development of production transform themselves into means of domination over, and exploitation of, the producers; they mutilate the labourer into a fragment of a man, degrade him to the level of an appendage of a machine, destroy every remnant of charm in his work and turn it into a hated toil; they estrange from him the intellectual potentialities of the labour-process in the same proportion as science is incorporated in it as an independent power; they distort the conditions under which he works, subject him during the labour-process to a despotism the more hateful for its meanness; they transform his life-time into working-time, and drag his wife and child beneath the wheels of the Juggernaut of capital. (my emphasis)
The despotism of capital is a despotism of time, which finds it locus on the labour process through the extraction of value. Of course this is not the only form of capitalist alienation or commodification, but time is, I would argue, its privileged vector.
Capitalism, therefore, negates our experience of time, subjects that temporality to 'capture' and deployment within the value form. This capture produces the effect of negativity in this relational 'friction' as a felt need. This is true of even the most anti-humanist forms of Marxism, as we see in this statement from Althusser's Reading Capital:
In the capitalist mode of production, therefore, the time of economic production has absolutely nothing to do with the obviousness of everyday practice's ideological time: of course, it is rooted in certain determinate sites, in biological time certain limits in the alternation of labour and rest for human and animal labour power; certain rhythms for agricultural production) but in essence it is not at all identified with this biological time, and in no sense is it a time that can be read immediately in the flow of any given process. It is an invisible time, essentially illegible, as invisible and as opaque as the reality of the total capitalist production process itself. This time, as a complex 'intersection' of the different times, rhythms, turnovers, etc., that we have just discussed, is only accessible in its concept, which, like every concept is never immediately 'given', never legible in visible reality: like every concept this concept must be produced, constructed.
Capitalist time is rooted in biological time, but not identified with it; it overrides and negates this time, creating a new temporal experience of knotted times, that are never given or legible as such. Hence, at least Althusser implies, the difficulty of transition from the felt need of resistance to an actual knowledge of capitalist time.
It is the immediacy of the relational extraction of value in labour that provokes resistance, which is vectored through 'lived experience' (historically conditioned of course), and through the necessary strategic knowledge of this extraction. This is why I would suggest the impossibility of retreating into some 'reserve' of negativity, but only its articulation 'within and against' the capitalist despotism of time, which is to say its strictly relational form.
Of course, the further difficulty is the fragmentation and destruction of the worker's movement, which did play a role in the development of capitalism through the valorisation of labour, but which did also, often despite itself or against itself, carry the utopian traces of the critique of labour itself. While we have individual negativity if you like, often in the truly negative forms of psychic or physical distress and suffering, what is truly missing is a collective articulation of this negativity. Here the labour process still, negatively, offers points of collective articulation in terms of collective resistance to the imposition of the value form, as would also consumption.