Build lots of content. Download some new character/rig from the internet and animate it, once a day, for one to two hours a day. Study what you did, and take notes for tomorrow. Focus on a particular area per month. One month it's secondary motion; another month it's facial expression; after that it's mechanical movement, and so on.
Look at a lot of youtube tutorials. There are both good and bad ones – see them all, work through them all, you can learn in each case. Also read some classes/courses/books/videos. Anything that lets you get insight into how other people are doing things!
Finally, once you have a very good insight into critiquing yourself and what the different areas are (from the books and tutorials) it will make sense to start looking at finished animated projects, and critiquing them, like you'd critique yourself, and then trying to re-make them with some fixes that you'd identified.
It's really a product of “how much time do you spend in the tool” times “how deliberate are you about practicing and critiquing specific skills.” So, not only do you need to do the work, you need to do the work of focusing on which parts to practice and iterate!
