Backtesting is a crucial tool for me, as it provides valuable data on the potential performance of my strategies before applying them in real markets. It allows me not only to optimize my strategies but also to manage risks and increase my confidence in my trading decisions.
I recommend doing backtesting at least twice a week, even if you are profitable; it is a very powerful tool.
There is nothing you can do that can guarantee your success, whether you are talking about long term or short term success, what backtesting can do is to give you the confidence of using a strategy that can be successful if used appropriately by you, albeit this assumes that you did your backtesting in the correct way, which is not a given as it is very easy to make mistakes at that stage and believe you have a great strategy when in fact this is not the case, a very dangerous scenario for you or any other trader.