Don't always play by the general principles

This game I lost is a great example of why you should not always follow certain general principles, such as trying to trade material off when you have a lead in material.

Well the point is that you did not trade material.

At move 10 you lost a pawn, that's not trading material.
And later you offerd to trade material instead of forcing a trade of material.

maybe im missing something but why not 21.Qe2

Yeah, you didn't try to force any exchanges towards the end. Some comments:

25. Rae1 would have forced a trade of rooks.

28. Bxe6 wins a pawn and destroys black's fortress while keeping the tempo, as far as I can see (28... Qxd1 29. Rxd1 hxg6 30. Rxd5). Instead, 28. a4?? surrenders tempo uselessly.

I'd prefer 17.Be3 not placing your King in a terrible endgame position (as far away from the center as possible); and then trying to relocate the QB onto the a1-h8 diagonal which is way better than being on h6 IMHO.

Instead of 19.Qb7 (following my personal rule: Grab first - think later) I prefer 19.Rad1 activating an inactive piece and putting it on an open file. 

The ending would make a good puzzle though and at least it was better than some third-rate back-rank mate. So at least you can take credit for making up a decent puzzle!

Please note that 22.Qf6 forces mate.  Black has to give up his Queen (22...Qd4) to prolong it.  He then has to give up his f-pawn, e8 Rook, and bishop to prlong it further prolong it.  Thus, as it turns out, 22.Qf6 is a forced mate in 6 moves.