Instruction, by all means.
Here’s a quick rundown of my journey:
I got my first (non-Airgun) handgun at age 15. I read and studied more, practiced, and dry-fired.
I started shooting handgun matches- .22 handgun silhouette- at age 29.
I stagnated for a lot of those years. Shooting silhouette gave me my first really noticeable gain in skill. It drilled into me the importance of focusing intensely on the front sight. If my focus began to blur even the slightest, it was a miss.
That game also showed me how ANY changes in grip can change the POI.
I started shooting USPSA at age 32, and IDPA soon after. They let me practice different skills.
But my first handgun class, at age 37, really opened my eyes.
In that class, I got enough correction in the first 20 minutes on the range to make a jump in my skills. I got more from that two-day $150 class than any of my self-teaching.
You really need another (skilled) person’s eyes watching you to see what you are doing. A good instructor can analyze your trigger control almost immediately, and that is where most people have problems.
Simply put:
Before taking a class, my practice sessions consisted of practicing flawed trigger work. To a slightly lesser degree I had errors in my grip and other things.
I didn’t know this before, of course. I just kept on doing it the flawed way.
Now, bad habits still creep in, but I see it. I know what to change.
Breaking the bad habits when they appear is something else, but at least now I know when it happens.