Besides, markup usually takes above two years of study and hands on experience before you start getting good and of course web accessibility is interlocked. Since the further one goes the less one knows.
I assume you are mostly enjoying those six hours of practice and taking breaks because sometimes a rest is better than constantly hammering away. In contrast I markup about one webpage per year. Nature does not hurry, yet everything is accomplished.
Well, at least it does look like you are aiming for layouts rather that pizzazz so that is a virtue. Presumably you have made some mock pages of your own interests. Then applied the CSS rather than just looked at demos and followed them.
You can learn CSS theory (of for that matter markup theory) purely for the sake or learning and understanding or you can both learn and apply it to real world scenarios, e.g. answering others forum questions when they are stuck with CSS, etc. You have to balance different strategies or you can lose focus of what you really want to achieve, wisdom and knowledge are different. There is no clear-cut answer and a lot of trial-and-error will be needed.
It is good you have the passion and seem to want to learn; good luck, remember if you are stuck with the certain CSS on a webpage the forum is here to support with such questions.