Your muscles are smart. We've all heard the term "muscle memory". If you've been training jiu-jitsu for a while, you've probably had the experience of your body getting to a certain position and then without thinking, it just reacts and suddenly you find yourself with an armbar (or anything else). It wasn't something you thought about doing step by step, it just happened.
When your body learns enough movements, it will start to find it's own way. Sometimes you won't even consciously know what you did...just that is was probably pretty cool and it worked...and if someone saw it and asked you what you did, you might not be able to answer them. Your body learns how to move...how to react. Training teaches your body what to do. Your muscles are smart and really do have memory.