For some reason when I'm working out, rather than fizzling out I just stop all of a sudden. For example, when I'm lifting I've been using a 5,4,3,2,1 set/rep plan, with increasing weight. For whatever reason, sometimes I just abruptly hit a weight I can't even move, without struggling too much on the previous weight.
When I'm doing BWE, the stop is even more pronounced. What could be the problem? Is it a lack of motivation, or am I maybe over-motivated on the first sets then totally spent out of no where? Thanks.