Knock on Wood
If ever a situation arises where I feel like I myself or someone else had jinxed something I say knock on wood then I knock on the side of my head (near my temple) then I knock on something wood if there is something wooden close by. If theres nthing wooden nearby its okay, I just say knock on wood and then knock on my head. The superstition is really a conversion superstition with the idea behind it being that this ritual will negate any jinx or superstition that was caused by something someone said. For example you could jinx something by joking that something you dont want to happen will happen.
I learned this superstition from a teammate on my high school basketball team. I dont remember exactly what happened but she everyone sitting on the court stretching and talking before the game and I guess someone said something that she though might jinx us so she said knock on wood and then knocked on her head then on the wooden floor. I never really thought of myself as a superstitious person, but I suppose performing this makes me superstitious. Superstitions often have a psychological element to them meaning they are performed not because they necessarily effect any sort of change in the universe or cause something to happen or not occur. Superstitions are performed by people because it make them feel better. For me personally I believe this to be true. I think knocking on wood gives me some peace of mind when I think something is going to be jinxed but Im not so extreme where it would freak me out if I was unable to knock on wood.