I'm not a very strong gamer at the best of times, even in my usual genres. At FPS I'm hopeless! But (I told myself) Sanctum is a tower-defense game, and I can play those okay -- the tower defense element doesn't require precise aim or quick thinking. I'll be fiiiine.
Well, I wasn't completely wrong. My mazing was good, and I learned pretty quickly which kinds of towers go where; I'm even slowly catching on about when upgrading is better than adding towers and vice versa. But it's hard to win Sanctum on the strength of tower defense alone. My personal best on Survival mode, which I set today, is Wave 12 in the Mine -- on Hard difficulty.
I pretty much know what I'm doing wrong. My "playstyle," which is a playstyle in the same sense that sitting on the couch eating potato chips all day is a lifestyle, is to stand on a block shooting my assault gun down at monsters, maybe occasionally tossing a grenade if there are groups of runners. When they've passed me, I teleport to another block and repeat. Shockingly, this lazy-ass strategy actually is good enough to beat every level on Normal. But it's not even close on Insane. When I first read the Insane strategies on the wiki -- for example, alternate between freeze and grenades while running backwards through the maze -- I pretty much gave up. Running backwards through the maze is hard enough. "Fire with the sniper rifle while the assault gun is recharging" is about as advanced as my strategy gets.
So now I face the choice: learn to play Sanctum for real, even when it requires a playstyle I don't have a knack for and don't especially enjoy, or else only play Sanctum on low difficulties (and never get those delicious achievements).