Consistently inconsistent

Hi so a quick intro I started surfing when I was 15 yrs old and now 40 years on at the age of 55years old get a few sessions each month , the problem is lasted pretty much most of my surfing years where I am an experienced and rate myself as a "good" surfer with a great deal of experience. My main problem is lack of consistency where one day I could be onto of things and surf well then the next day and more surf like its my first day out a real beginner, not sitting in the right place , catch only one or two waves that session but either fall on basic take off or have no idea what my body is doing no co-ordination at all. I have a good quiver different boards like a soft board also to keep me catching waves easier when they are not sk good it's very frustrating and even depressing when i go through this, like 1 good surf - 5 bad ones. Any advise for consistently inconsistent
Many thanks
Many thanks