Read the book Pit Bull by Marty Schwartz. You will read a story near the end where Schwartz trades OPM, and nearly kills himself from all the stress. Not suicide, but he is literally dying in the hospital from all the stress he put on himself for results. The book is a good read for other reasons as well, worth reading as an educational book on the life of a trader.
The value of papertrading/simulation differs between testing a 100% mechanical system and a discretionary trading approach. If the mechanical system is automated and fill assumptions in the papertrading/simulation are reasonable then there is some value. However, emotions do strange things to people when money is on the line. All those nice discretionary profits can evaporate when your heart rate triples and your fight or flight instinct kicks in. The greater the % of discretionary judgement used in trading, the less value papertrading/simulation has IMO.
And if your papertrading fill assumptions are not valid then papertrading can actually lead to harmful expectations when real money is put on the line.
Also do a search on papertrading and OPM. These subjects have been covered hundreds of times.