Start small then build up. Give yourself lots of small nonsense throw-away challenges, or maybe take one small part of somebody else's website and see if you can duplicate it.
You have to keep challenging your boundaries. Don't do stuff you know, try to to do things you don't know. But keep each step upwards simple - don't try to build a skyscraper before you can build a house.
I think this is great advice. The only thing I can add from my own experience is - take your time to reflect on what you've learned once you achieve a new goal.
I also sometimes like to redo old stuff without looking at the code of my old solution and then compare. It is time consuming but really helps to see how you have grown.
You have to keep challenging your boundaries. Don't do stuff you know, try to to do things you don't know. But keep each step upwards simple - don't try to build a skyscraper before you can build a house.