Superstition

Crossing your fingers when you lie is telling yourself that you're allowed to lie because you're a Christian.

That is just one of many superstitions religious people have. It stems from belief in the unprovable... belief for the sake of believing.
If you can believe without proof in an omnipotent being that created the universe with mojo, you can believe anything.
Superstitions are training wheels for religions.

I do not knock on wood.
I walk under ladders if it's safe.
I open umbrellas indoors.
I do not cast bones to make decisions.
Found pennies are not lucky or unlucky.
Black cats cross my path and I don't care.
I spill salt and don't toss more over my shoulder.
Breaking a mirror does not give 7 years of bad luck.
13 is just a number between 12 and 14 and should be a floor number in tall buildings.
A shiver is not someone walking on my grave.
I step on cracks and my mother's back is unbroken.
Four leaf clovers are plentiful.
Blessing a sneeze does nothing.
Horseshoes protect horse's hooves.
Rabbit's feet belong on rabbit's legs.
A coincidence is not a sign.
Everything does not happen for a reason.
I don't believe in gods.

Superstitions are for those who do not understand how things work and do not question absurdities.

At worst, superstitions cause people to believe in absurdities as training for religions. At best they are a trivial version of Pascal's wager.