It seems that even after a day of really hard training, I still wan't to go hard the next day, even though I know I need to rest. How do you guys convince yourself to reset?

I injure myself. Works every time.

Depends what I'm working out. If it is different muscles then okay but not the same muscles. In the beginning I could work out all of the time and even now sometimes I can but most times it will catch up to me ... especially with martial arts training during the week as well.

Then overtraining comes into play and that is followed by weakness, results going backwards, feeling ill, getting sick, and injuries ... and a whole lot of other effects that are not positive. If you can do so now then you need to ask yourself will it benefit you or not and then go from there. Everybody is different so what works for one won't work for another BUT if you lift smart you lift for life. You don't get too burned out as we all get this way one time or another.