If that's the case, you have tested the strategy on limited data. It should be tested for all types of days. Down, up, sideways, gap up , gap down, sudden reversal etc.
Personally, I test strategy for 4-5 years using programs. Even after that, I am not able to handle drawdowns and I end up going back to gambling. I hope I will get out of this habit and stop taking contrarian trades(Glenmark recently).