I journal every day, and I've published ten books.
I find it works all different ways.
Sometimes an idea comes - I've learned - write it down and keep the flow going.
Sometimes, the fingers fly on the keyboard, and I see what I'm thinking afterwards.
Sometimes, the words and thoughts come at the same time.
Logically, there are no words without thoughts, but our first experience may well be that the thoughts arrive through keyboard or pen before we are aware of them.
My suggestion is - whatever way it comes, let if flow. And if it isn't flowing, show up at the keyboard and blank page, and either wait expectantly - or just start writing.