One of my favorite riddles is this:
What is the difference between theory and practice?
Theory is when you know everything about it but it won’t work. Practice is when it works but you don’t know why.
It seems to me that good composers are always concerned with both theory and practice. They not only compose, but they also think a lot about how they are composing and why. I sometimes even recommend to younger composers that they make a trip to the library once in a while. Study some idiom carefully before you try to write your parody of it. Study what other people have already done before you try to compose chance music or serial music or graphic scores. Try to avoid reinventing the wheel.
And as you approach 60, it can be an excellent idea to sit down and try to explain verbally the specific techniques you have used, partly to help others understand what your music is about and partly just to clear out your own jumbled memories and figure out where to go next. I spent almost a year writing a purely technical book called Self-Similar Melodies (1996), and I feel this has clarified and deepened everything that has come since.