If in a situation you can't run away, kick them in the knee. Not the balls, the knee. And not like a ball but look up videos on a front kick. Set aside some time to practice that. Most thugs are men, most men reaction to a kick, is to protect their balls so a kick to the knee should catch them off guard. This is 2nd to last resort if you truly can't run for whatever reason. If they catch your leg, you had no chance anyway. If in a country like the USA get a gun license, buy a handgun and practice that but also the kick. Weapons like a knife require you to be close, close means you can be grabbed, you do not want to be grabbed by a stronger person. Knife is useful if already grabbed though, so carry pocket knife if legal(or illegal if you fear they don't just want to rob you) but stuff like that is true last resort.