We often read on numerous forums about how much a retail trader should risk per trade and the majority of forums advise risk per trade should be between 1 to 3%. However, I think the best way to gauge your risk tolerance is to place a trade overnight with a reasonable amount and see whether you are thinking about the outcome of that particular trade while you are in bed. If you are worried then obviously the amount you risked is above your risk tolerance and it's time to lower your risk until you are sleeping without being worried.