Life appears spent performing trivial routines, achieving nothing of any significance.
Though A and B continuously step from frame to frame, compulsively driven to go on, the only progress they make is to move through linear time. Neither can ever accomplish anything significant. Life goes on, repeating endlessly. Nor can either withdraw into inaction for long. The players remain unaware that stasis is the natural lot of man, or else the introspective A would surely abandon his prayers. Indeed, as the mime portrays, it is some unrelenting malign force that brutally goads man into the never-ending monotony of his pitiful existence.
In his reading of 'Le mythe de Sisyphe' by Albert Camus, Beckett discovered a symbol for the futility, frustration and absurdity of all man's labours. Sisyphus - one of classical mythology's great sinners - suffered eternal punishment, having to perpetually roll a great stone to the top of a hill, only to see it roll back down again. Being born to enact and endure eternal cycle of arousal-activity-rest, without any meaningful progress being achieved, is the sin that afflicts A-B.
The viewer may judge how appropriate and successful is the filmmaker's sepia-tinted 'silent movie' treatment, with its flickering human animation.