Relax, let the drag do its job, dont panic. It takes losing a few good ones to know how to land good ones. IMHO the 36in to 41in fish fight the hardest and longest. The big ones, sometimes a few long steady runs, sometimes think its a schoolie.
I also learned of a way to turn a fish that works suprisingly well. When a fish makes a run toward a rock and pulls line steadily it has its balance or "has its head". Most when fighting a fish, pump the rod in one long pull and then reel to try to get the fish in. I feel in a situation like this that if you make a series of short pumps and quick reels in between, you constantly knock the fish off balance and you can easily turn the fish even with lighter tackle. Its hard to describe, but it does work.