try playing one game at a time, or give your wife $10 every time you lose .... or take a day off after every loss, or something but introduce some sort of "punishment" for lax play.
How to slow down
I have had the same problem and i like lecycliste's suggestion. It does no good to beat yourself up about missing a good move because you went too fast...the ego loves you beating yourself up and you create a fictional identity that "I suck at chess" and it helps you not at all.
I will try lecycliste's suggestion myself...It cannot hurt! 
HERE HERE!!! Same mistakes. I even make the move and then as soon as I hit the submit button I realize oops thats mate on me, or there goes the queen. I guess I didn't need her anyway. I think chess needs a new feature like mario cart. You step on a square and then you get auto pawn promotion or regenerative powers or your opponents pieces all the sudden can only act like a king piece or something. Just to keep it lively. I know how about like in the show duel you can press your opponent into having to make his move quickly.
I think I can weigh in on your problem Thompson, because that was me for the longest time, only recently have I changed. I used to play multiple games as quickly as I could, just rotating through them. The truth is I got a rush off of speed kills - whereas I did kick myself for losing games, I got more of a kick out of inflicting them; kindof like rapier blades clashing ("Take that! And that!"). This was well before live chess came a long, of course, and now I'm able to more effectively seperate them.
I think what might cure you is just time. Keep playing however is most fun. The fact you made this thread means that the losses due to carelessness are starting to annoy you more than the speed wins. Good! I remember I used to think that "slow" chess, or taking your time, was waaaay too boring. I thought I could just get instinctively good, and learn how to intuit good moves through experience. It's not really the case.
You don't have to make it seem regimented as in "pick X number of candidate moves" per say. Here, let's make a deal. For the next week, everytime you enter a game, before you're allowed to evaluate the position, crack open the analysis board. Force yourself to. That's all I'm saying, then whip some speed combo's off on it. Just try a few variations. Trust me, this will keep something of the speed and draaastically reduce blunders. Force yourself, eh? And in a week post here and tell me if it changed anything for you.
Good luck man!
Oh, and one thing to add that might help you to slow down more also: imagine that your opponent is being very cautious, taking his or her time. Working with the analysis board. Imagine they intend to take all the time in the world until they unlock how to crush you.
I do the SAME THING!! I hate it. what I do now is when its my move I look at what was moved, then revisit the last 5-8 moves to familiarize myself with what has been played(maybe an idea pops up), and then come up with a response or two, and finally WALK AWAY. Come back in a couple of hours, or longer (maybe a day?). Then come back, repeat all the previous steps and see if my initial response will be the same. If so I feel much better about hitting the submit button. If I come up with a different response that I did not see before, I might repeat All the steps again until I feel comfortable about my move.
This is what I do when I am playing someone who I know will make me pay heavily for blunders. If Im playing a lower rated player, I MIGHT just go through it all once.
The key is to come up with a response and walk away for a bit. ITs the best way Ive come up with to keep me from playing too fast (so far). This process has saved me a number of times from playing a flat out blunder:}) Anyway I hope that helps, Good Luck!
Here's something Ive been doing to which has helped slow me down. Unless next move is forced or obvious, I don't make the move the first time I look at the board. I look at the board, decide on a move, and put it in my notes. Then, I move on to the next game, do the same thing. Either the next day, or after 10 games or so. I start back through the list. This time, I start the same way, I look at the board and decide on the move. Then I look at my notes, if the two moves (the first I wrote down, and the one I just decided on) match, I make the move. If they don't, I write the second move down and move on again. When I come back the third time, I don't have a pattern for how I handle it, but by this time, I've already spent a good deal of time looking at the board, so playing too fast isn't an issue.
I am currently going through the exact same thing. Now that I am playing stronger player, I realize you have to take your time in order to be competitive.
For me, I am going to finish the games that I have going on. After that, I will limit myself to 1-3 games at a time. That way, I will be forced to focus on those few games and hopefully my level of play will become better.
There's no worse feeling in chess then to click the submit button too soon just to realize that you overlooked someting.
I suffer from this at times. I have just had to force myself to slow down. Good forum and replies.
I also suffer from this. Analyzing my games is a dagger in the heart for me. It often shows me how I've completely blown winning positions and mist clear wins simply because I was playing to fast and not looking at the whole board. Thanks for this thread. Very helpful suggestions
I have recently started playing chess again this year. The biggest problem I have is that I keep playing far too fast. I tend to play the openings on auto-pilot and find it hard to just stop and think for a minute or longer to play most of my moves. I know I should stop, spend time looking at what the opponent has just played, study the whole board, choose at least 3 candidate moves, don't play the first move I see automatically, calculate several short lines of play and check for blunders.
I know all this and I still play like a moron and just play what I feel like half the time. Two reasons I think I do this is that I'm just lazy and I play primarily against computers, which shoot out their moves pretty quickly.
Has anyone else suffered from this problem and does anyone have any tips on how start playing more sensibly?