Hitting a wall when training?

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.

Motivation.

When I train on my own at times I can't be assed and the weights just feel heavier.

When I train with guys around (most of the time) as I lift better the weights feel 'light'.

But I don't really hit a wall like you. I just don't lift as well.

Take a 10 day break and come again feeling hungry :D

Koing

I noticed this morning that I gave out right about the time I was thinking "I wonder when I'm gonna give out?", so I'm pretty sure you're right.