I really can’t seem to grasp the creative element of colour grading, I get the technical idea, but I cannot for the life of me put this into practice

Basically as the title says, I understand the basic concepts behind colour grading (I know what each slider or curve will do to an image), but actually using it is a different beast. I’ve been trying to practice it and everything comes out worse than the original footage. The whole creative side of it seems completely lost on me. I work with a guy who just seems to know it, he just does it and it comes out perfect, he says it’s all in the feeling and just going with what looks good, but I cannot make anything look good.

Does anyone have any suggestions on how to get over this. I practice it so much but it never improves.