Good to great?

What were the biggest realizations/strategies that transformed you from good to great?

I am consistently getting destroyed in DE. In TAD I was lvl 13, often played 2v2-3v3 against a variety of opponents, and was a solid teammate. Now I am playing more 1v1 in addition to ranked team matches and always lose. Setting all issues with match-making/ranking aside, what would you suggest I do to elevate my game? (I play as British, but all civ recomendations are welcome so they can benefit others.)