Going heavy calls on adrenilin, which in time will prove catabolic if there is not sufficient rest between heavy workouts.
That is easy part to know; you have to design workout in line with your ability to recover. Will vary from person to person.
Some people, like me (highly strung), need a lot of rest (i keep max efforts or sets to once a fortinght). Others can back up twice a week.
Key is when you do go heavier, you get an improvement. If you dont, your training is not working.
If you do want a guide through a test, give yourself one week lighter to ensure you are ready for a max potential performance, whether ti be low or higher reps. Aftert all, one can go very hard on lighter weights to failure, and still be exhausted. By light, i mean well within yourself and nowhere near failure.