I've had to look back at some recent games because I've lost some in ways I didn't figure out right away or that were just particularly stupid.

#1 -- sacrifice ambush

http://lichess.org/analyse/kjp3v40o/black

I had pretty much shut my opponents bishops off on move 5 but I then had to put quite a bit of resources on keeping safe the base pawn on F5 and ended up being quite passive altogether. What ended up killing me was the idea of a) getting my queen moving through the big diagonal that it did share with the opponent's bishop but which I nevertheless thought was safe because of that little barrier of pawns way up in my opponent's territory -- as well as b) getting castled in that same corner targeted by the white bishops, which, again, I thought would still be safe.

No, dude. 16.Nxe4. All downhill from there.

How should I have taken such a sacrifice into account? The clue, I suppose, is that exactly because I had put white's bishops into such a nasty position, I should expect my opponent to put something a bit more elaborate than the average planning into how to get them free. An additional data point: Here's how the Stockfish engine played the game from move 11 onwards instead of going with the queen development idea I used. Note that white still makes the same sacrifice even though it can't use it to threaten the queen. Now black wins.

http://www.chesspastebin.com/2012/07/04/unknown-unknown-by-tsinnema/

(Even though chesspastebin, AFAIK, doesn't really support chess960, I was able to display this one because it happened to not have any castling.)

#2 -- stupidest checkmate ever

http://lichess.org/analyse/e0julc0i/black

If you look at this, I really don't need to explain anything.

I guess you could call it classically tragic though. The knight's return from a heroic journey ends up condemning Black to a humiliating defeat.

#3 -- only dull moves available -> fail to decide -> waste time -> blunder in a hurry -> lose

http://lichess.org/analyse/ph3kocgm/black

Around a few moves from 12 onwards I spent a huge amount of time simply not managing to pick a move. What happened later, once I was already badly behind on time, is pointless to talk about but I'm wondering what I should have been focusing on in these couple of time-consuming moves.

On move 14 I ended up picking Qd8, to make it available for some action in the h-side, but I didn't really have much of a clear attack plan, since white had a lot of defenses available. On one search on Stockfish this actually was its favorite option up to depth 12, after which it settled simply on Nd4. The primary advantage of Nd4 seems to be not that some direct attack is made available on the king's position but rather the immediate pressure being put on f5.

How would I better be able to look at the right aspects of a position like this (including the possibility that I really should just make some sane move, any sane move)?

I could've avoided that particular unpleasantness by doing better on the other big time-consumer, 12...b6. 12...Bb4 was clearly better.