Blitz vs. Tournament vs. Correspondence Chess
I've moved around alot over the years but always end up nearby NYC. And I see many of the same blitz players year after year in the parks & indoor spaces where people play chess and... they don't seem to get much better.
I find I improve the most when involved in regular OTB (over the board) tournaments, which, ironicly are somewhat hard to come by in & around New York (and the ones that do exist are ridiculously priced, around $40 or so with tiny prize funds). Coorespondence helps too but it's not the same intensity as a long OTB game & it's hard to get as pumped up over an e-rivalry (though definitely possible ).
Blitz is the junk food of the chess world. Can be fun for a break or just for the rush of it but a steady diet rots your chess mind. The decisive factors are usually all about taking the time to calculate the critical variations & in blitz there simply isn't the time. GM's can play masteful blitz & make it look easy but we're not them & we won't get to be them by gunning out unexamined game after game.
Feel free to debate me. I like alternative viewpoints. Analyzing all your blitz games may help somewhat but I still say it's better to play 2 or 3 slow games (G/60 or more) a week than 20 or 30 (or 100) blitz games.
Studying probably (I haven't been able to try it ) pwns all. If you have the discipline to study nine hours for every one you play you'll probably advance fast (assuming this nine hours isn't of the course of nine months... or years). If I can study 5% of how much I play I'm doing well.