I think what you need to improve on is you DEFENSE.
How can you defend without knowledge of tactics?
Of course one can not defend without knowledge of tactics.
Except that when anyone talks about tactics it's all about Offense - winning material
Not Defense - avoid losing material.
A perfect example is this game of yours after 15.Qc3 (see didagram left)
Black played 15...Nb7 and after 16.Qc6+ Ke7 lost the N to 17.Qxb7.
Defense oriented would have seen the fork (Tactics) and played 15...c5 instead of 15....Nb7
How many examples are there in Tactics Trainer that illustrates Tactics to avoid losing material? Most, if not all examples in Tactics Trainer is all about winning material - not avoid losing material.
If you are familiar with attacking pattern for gaining material, you can foresee such intentions of your opponent. You can sometimes see the threat only if you know its pattern. So my opponent should be familiar with simple fork threat and understand, that his pieces can't move to certain squares, and would deal with it properly. Though I must admit, there are very few purely 'defensive' tactics in any TT.
I really don't feel that tactics trainer helps me at all in my chess games. I often don't even notice the best move in these situations. I just end up doing all the tactics really quickly and not paying attention, just trying every forcing move. Sometimes, I try to do it more slowly, and that works fine for the rating on tactics trainer, but in practical chess my tactics aren't going anywhere.
Are there any books that can help one's tactical ability? Please don't suggest puzzle books because I have a bunch and that hasn't done much. I'm playing in a tournament soon and there will be a chess store there so I might be able to find the book there if it's well-known. I have trouble finding the things that are outside the box. In retrospect, it's always so easy to say, "I should have gone there because it allows me to win a piece without having to deal with the pin" but in the game I don't see the moves. I have a good example I can post of one I missed.