Definite: My hair requires brushing more than once per day.
Definite: When coming home after dark on days when it has rained, I am going to step on snails no matter how hard I try to avoid it.
Possible: People you like don’t always like you back, and you don’t always get to know why.
I initially misread that as people might not like your literal back, and was imagining this kind of crab walk where you tried to keep your back away from everyone because, hey, assassins everywhere.