Keep the beginners mind, curious and humble! Don’t ever get to the point where you think you know it all. You can’t, it’s impossible!
Beginner’s Mind is really important to the creative process, at the easel and in life.
For me, summertime is a time to learn new things, usually not directly related to my art because feeding my curiosity always reaps benefits to my art practice.
Where can you take free classes? Here’s a great place to start: http://academicearth.org/universities/