An exercise I learned in painting class years ago is to try to copy a master. Now that I am teaching, it's so fun to challenge students with this exercise. It can seem intimidating at first, but it's often surprisingly successful.
What is so fantastic about this exercise is that a lot of the decisions have already been made for you. You don't have to think about composition, or plan what to paint. You have to match the colors and values but you're following what someone else has created, so it takes some of the decision-making out of your hands. This is great for beginning and intermediate painters.
Last December I had a student knock me out with a copy of a Van Gogh. Silvia found a way to match the colors very successfully, even while using modern acrylics instead of oils, and she captured his signature brush strokes. It's so fun to teach and be blown away by your students can create!
Stunning. Right? Try this at home! It's a fun exercise. Challenging for sure, but somehow freeing as well.