Movement of light, figures, waves, or anything, and painting it from life:
I think whenever you have the fear 'I can't do it' just like I have from time to time, you should go ahead full force. Just do it. Give it a go.
You might think nothing of the end result. Put it away and be surprised 2 weeks after. Often 'doing it anyway' will prove itself. The effort, 'the try' alone is already enough as a first triumph over this 'mental hurdle'. Because, of course, anything can be painted.
Never scrape a painting unless you are absolutely certain it's a (half-finished) sure fail. If you can complete it, but you don't like it, don't break it then and there. Just bring it home, let it dry and look at it again later in time.
Don't scrutinize 'failed' paintings by having them in your sight 24/7. That's just not helping you. Put it away to dry (somewhere flat, in a drying cabinet) and always focus on the next painting you're going to create.
Here an image of my equipment there, a few big brushes, one or two smaller ones, a palette knife, cloth, tin can, the cigar box easel, the leftovers in tupperware, duct tape. I only had a very tiny bit of turpentine, that was gone soon, so most of the paintings were painted without any medium or spirit.
I teach about painting Seascapes in ► Seascape Beginner that's here and an online course more specific about Summer seascapes, figures and parasols is this one: ►Painting Summer Seascapes find this here.