My Sensei was having us become really tired at a seminar and told us that when people are tired their muscles relax and their throws improve.
Drift alert ...
IME when this tired phase happens uke just stops giving 'real' attacks so as nage I can get away with garbage that normally would not work at all. Things do 'seem' to work better/easier but when I look objectively I just see the collusion factor escalate through the roof.
The only saving grace to the type of training (that I can find) is when so depleted I focus more on how to move myself and tend to just ignore uke - this can have lasting effects but this method is certainly not very efficient towards that end.