Don't beat yourself up when you find yourself in a creative black hole, know that you can beat it. It may indeed be hard, but it's not impossible. And if someone tells you they've never had a creative block, they're lying. Everyone has them at some stage, it's how long they last that differs.
1. You’re Setting Unrealistic Expectations
When you’re in a creative block, you stop producing. When you think of painting again, you think of the finished paintings you were proud of, and forget the work involved in producing them, in getting to that standard. So when you to start painting again, you’re frustrated that you don’t immediately get the same standard of results. It’s unrealistic to expect this of yourself. Dig out some of your failed paintings to remind yourself that you never only produced good pieces.
2. Your Skills are Rusty
Painting is like riding a bicycle, you do indeed not forget how. But that’s not to say you’re wielding a brush with the same level of skill as before. Technical skills do get rusty with disuse.
Take the time to do those Painting 101 exercises again, such as the painting of a color triangle and then expand it by painting up one with each of the reds/blues/yellows you’ve got. Familiarize yourself again with the way specific colors mix, with the way individual brush shapes make marks. Fill at least a spread in your sketchbook with technical practice every day.
3. You’ve Forgotten the Joy of Creation
Painting isn’t solely about producing a final result that will sell. The act of creation, the mixing and applying of the paint, the choices and decisions made, the "I wonder what will happen if I..." moments, these are what makes painting an enjoyable challenge, not a mundane job. Allow yourself the time to create and explore, quit obsessing about getting a "good" end result.