I think the problem is that, like you said, you checked out mentally. When you play this kind of BM deck, you need to be aware of what your opponent is doing. You want to get half the points slightly before he can. The more he's going to build, the more you can build.
Turn 7 you should have put back a Silver and bought a Gold. Then you buy your turn 8 Province without using the coin token. By declining to use your ability to put back a good treasure, you're hurting your next turn in order to buy a more expensive card this turn. But a Province is not so much better than Gold at this point.
Turn 12 and 13 you don't want Islands yet. The game is not about to end unless you can end it, and Islands are not going to help you.
