I finished my participation at X-Wing regionals in Seattle today. Over the span of 4 years, I went from placing dead last to making the cut at one of (the?) biggest regionals, and I believe I have a few things to say about gitting gud.
#1. The game is the game.
Perhaps you think that barrel roll isn't a real "Barrel roll" (it isn't) or that there is power creep pushing out legacy ships in favor of new releases. Maybe yes and maybe no, but while it may feel good to complain about it, it's not going to improve your game. The game is what it is, and you have to adapt to it, instead of resisting it while putting together your list.
#2. “If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.” ― Sun Tzu, The Art of War
I will risk sounding like a pompus *** and quote Sun Tzu here, because it's **** true of wargaming. I can't count how many games of Warmachine I've lost because my opponent would pull a combo on me, wreck my s*** and I'd be standing there with a puzzled look on my face. Know the meta. Play the meta lists to discover their weaknesses, and play against them to discover their strengths.
If you don't know that Ezra stressbug with Hera is going to pull a 3K while stressed and catch your ship with a snap-shot, you're going to have a bad time.
#3. Practice. Stems from #2, but also you need to practice your list so you don't forget triggers and abilities. Knowing a list is very different from playing/playing against a list, unless you have some kind of computer brain that remembers everything and can sim a whole game in your brain with a realistic opponent.
#4. Obstacles and setup. It's been gone over by better players than me, but I'll add this. If you don't have a plan for obstacle placement, at least try to put a couple of obstacles on your opponent's side of the board, at about 2&1/2 range away from their edge, to break up their approach and "funnel" their movement into one of three predictable "lanes".
-Pew pew