Hi,
It's an undeniable proof of skill issue, the battle system relies heavily on your base stats and dice rolls, so to increase your chances simply run a lot to gain more stamina, increase base stats (dex/int/cha) and pray to the RNGesus for lucky rolls.
Cheers
P.S. 150 stamina is very low, you should go running more often, even if your ass gets beaten, but it's the only way to permanently increase the stamina limit.