Running out of gas

I don’t know what it is but lately I have been having a tough time finishing the workouts. I don’t know if I am not eating enough/Well ? . I haven’t gained any weight but maybe it was that 2 week break. I guess It’s sort of like starting over again partially? I just got to about 8 min left in Chest and arms and I couldn’t do any more push ups… My arms starting giving up on me. I guess I just have to keep trying.