Why can't I remember my iPhone password?

I just got in it today. But then all of sudden after band practice I forgot it.

But then I typed it in later without thinking abt it and then now I can't remember what I typed in.
It's like muscle memory because I don't really think abt typing it whenever I sign in to my phone.

But what can I do to maybe jog my memory? To get it back

Write it down, and don't be an idiot.