Hi! Seems we are roughly the same strength (unless you are talking of a 1400 BLITZ rating, my blitz rating is sinking lower every day

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Well, the best way to find out what to study is to find out what you are doing wrong. Analyze your games and you will see. If you are losing because you are missing tactics, study chess tactics. If your position gets worse gradually without any obvioyus reason, my guess would be that you might want to look into studying chess strategy. But in any case, analyzing your own games will probably improve your game - in the long term at least.