I think it's what you do
beforehand is what increases your chances of landing that fish, and there's a lot of luck involved after the fish is hooked that you cannot control.
I have a habit of not re-tying and checking my knots, especially when the bite is slow. I can't count the number of times I've spent all morning and afternoon flogging the water, and I finally get a good bite at 4 pm and I set the hook only to have the fly-less fly line sail right past my face because the knots I tied at 8 am had become weak and I either broke off at the fly, or the tippet/leader connection.
I fished the Madison in Yellowstone in October a few years ago, and I managed to leave all my 4x and 3x tippet at home, and had spools of only 5x and 6x on me. Apparently, I had caught the river at the time where the big rainbows from Hegben had swam up. On one of my first few drifts, my indicator hesitates suddenly, and I set the hook. And a 24" rainbow rockets from up the depths.
This wasn't your typical rainbow I was accustomed to.
I was running a Hatch 4+ whose drag is pretty good, and the fish took off on a blistering run all the way through my backing. (First time I've seen that since it was installed.) The drag was set perfectly as to give the fish ample room to run if it needed to, and ample braking to prevent it from doing whatever it wanted. The knots had just been tied, and I'm OCD when it comes to them, and the leader material I use I have the upmost confidence in.
When trying knots, if the knot isn't laying down the way I want, I will snip off and try again. I had scouted the general area and had a good idea on where the most amount of current was, and where there was some slack water. I also knew where I could step and not step, if I had to make moves upstream or downstream.
For the first time ever, I realized that having my rod straight up couldn't get me much leverage on turning the fish's head. That is when I soon discovered the 'side pull' and got the fish's head turned, and headed towards the slack water that I had already found before I had made my first casts.
I mentioned 'luck' being a big variable in landing these larger than average fish, and luckily, I had no clear obstructions (rocks, fast water, downed timber, etc) so I was fighting the fish in open water. Of course, having a trusty Sierra Net's net at my disposal assisted in the final landing.
I hooked half a dozen fish that size that trip, all on 5x. Definitely a trip to remember.
Remember those knots, quality line, and sharp hooks. Increasing your odds with the variables you
can control always helps. When you do hook up with that 'fish of the trip,' it's your only connection to you and that fish, because once you're hooked up, you can't do much but hope the preparation made before that cast was enough, and hope Lady Luck is on your side.