Superstitions influence the lives of people greatly because superstitious people believe in signs of good or bad luck and they blindly follow those superstitions.
It really depends on what you mean by superstition; for example, many atheists and agnostics would call religion a superstition. Clearly, religion affects people's lives, but religious believers don't class their belief as a superstition. There is also a fine line between superstition and mistaken beliefs; for example, gamblers often have a belief in a "lucky streak" or being "on a roll". Statistically, it's well known that previous success in games of chance doesn't make future success more or less likely. Whether you call "lucky streaks" as a superstition is difficult to say. More conventionally, in the west, people touch wood or knock wood to stop bad luck, throw salt over their shoulder if salt is spilt, avoid walking under ladders (although there is some sense in that if someone is painting up the ladder!)