I am 35 and getting back into chess do you have any tips for dealing with the stress of defeat?
dealing with losing

It's part of the game. In an worlwide pool like this one you'll always win and lose. The main target should be keep improving.
Losing games is just part of the game. I imagine that most players lose roughly the same number of games as they win - assuming they are playing opponents of roughly the same strength.
As they increase in strength... they will still be losing about as many games as they win, because the opponents they play will be stronger too!
Don't take the outcome of any particular game to heart. You could perhaps "innoculate" yourself against the sting of defeat by playing significantly stronger (+200 points) players... as you would know going in that you were very likely to lose the game it might not matter so much if you do.
I play most of my chess at another site and have over 2400 losses there (and a slightly higher number of wins); I still don't like losing, but any loss I suffer is just another grain of sand on the mountain!
If you really need to get a win you could just wait for the opportunity to play someone 100-200 points weaker, it's not very glorious but a win is a win.

there must not any stress for losing ie a fear of losing go beyond that line and explore the beast in yourself, a man that is so fierce that no defeat can let him down. Try to adapt and improvise from your defeats rather than getting frusturation. Dont treat losing as a failure,, not understanding the cause of your defeat is a real defeat.

After I lose a particularly frustrating game, it can be useful to go back a view it, then leave a comment on why I think I lost the game -- even it if is just to comment on the frustration of losing on time (again...).
http://www.chess.com/livechess/game?id=1208958545
You might even do some productive analysis that will help you learn (though in my case this is rare!).

So I only have 50 games played on here but I cannot go to bed without a win. I am fortunate to have more wins than loses up till now but I've seen some people on here with like 900 losses and 400 wins, and I don't know how they handle defeat so easily.
I am like you, I need more wins than losses. But then my rating is low, because I play against weak players. It depends on how I lose. Yesterday I managed to capture my opponent's Queen, but then I lost. He is very good at plotting checkmates. My ego was badly bruised.

There seems to be a correlation between effort and accepting losing easily. Those that don't try very hard or don't expect to win take losing quite well and vice-versa. It's like the saying goes, "show me a good loser and I'll show you a loser." For those that do make an effort and still lose, they key I believe is to not beat yourself up because that doesn't help, but to examine the cause of the loss so you can grow. When you make the effort to do this, the stress goes away and you feel empowered because you know you've learned from the game and will come back stronger next time.

Seems to me the OP needs to quit playing until he gets comfortable with the idea he won't win every game. There will always be someone that can beat you no matter how good you get.

Beating yourself up just leaves you weak and stressed. It's much more productive to calmly look at the cause of your loss than to stew in anger. Just my opinion.

I see what you're saying. I'm not saying losing doesn't hurt. I'm saying don't make it worse by beating yourself up and reliving the agony. Try and detach and look objectively at what you should have done. This is the best way to repair your game and fix your emotional state.

Chess was Fischer's lively hood. For the majority of us, it's just a game. It's okay to channel ones frustration into motivation for improvement but if losing prevents you from enjoying the game itself, its time to set it aside for awhile.

I agree losses should hurt. But don't forget life hits much harder, as Rocky Balboa would say. That's what I like of this game, is somehow comfortable.

I recently got back into playing after not playing for years and I definitely believe that the rust has affected my play...specifically my patience and "feel". I have been pressing for attacks (usually when I have other things going on in real life) when there really is no attack to pursue. I personally am just going to scale back the aggression a bit and go back to basics.

If I have played well, but my opponent played better. I have no problem with losing. Try to learn from the game and do better next time. What really 'cuts' me up, is when I lose from an oversight or making a 'lazy' move and beat myself. The reverse is the same, I hate to win games were my opponent has made an obvious blunder. Many good games spoilt by lazy thinking.

The only difference between losing and winning if you play people in the same rating range (+200, -200) is most of the time blunders and if you accept that blunders are part of the game its very easy to overcome your frustration.

do you have any tips for dealing with the stress of defeat?
You need to accept that at whatever level you finally play at ...ie your best, you will be losing about 50% of all your games assuming you are playing opponents of the same level as you.
Once you understand that fact and accept it as part of the game, you will cease to be stressed.

I agree losses should hurt. But don't forget life hits much harder, as Rocky Balboa would say. That's what I like of this game, is somehow comfortable.
Did Rocky say that? Or are you merely suggesting he would say that? Sounds more like something Paulie would say as he drinks from a crumpled brown paper bag and stares you down.
So I only have 50 games played on here but I cannot go to bed without a win. I am fortunate to have more wins than loses up till now but I've seen some people on here with like 900 losses and 400 wins, and I don't know how they handle defeat so easily.