D17

I guess this is on topic to a degree. But whilst doing circuit training, or regular weight training, but mostly for circuit training. What mindset should I have to keep myself going 100%? As alot of the time, about half way through I drift off and only put about 80% effort in on and of during it. Get the typical 'f**k it' mindset towards the end of it. I try not to beforehand, but it just overcomes me during it alot.