From what I heard, flu shots could help those with naturally weak immune system but for most people or those who never get sick, flu shots do not make too much sense. But the key thing with the flu shots is, you either never take any or take it every year, otherwise it doesn't do much or any good...

Get adequate sleep, eat well, do not stress to much or find ways to relieve stress, wash/disinfect your hands several times a day, do not stay in confined places during flu seasons with people who appeared to be sick and you should be fine.