You've gotten some great advice here:
1) incorporate automatic stops/brackets
2) focus on one/limited instruments
but the biggie for me is that you're escaping addressing your failure to jump out of the losers, when you *know* they're losers.
You're married to the trade. But, WHAT WOULD YOU ADVISE SOMEONE ELSE TO DO IN ANY GIVEN TRADE?
You say you're good at making money, but in fact you suck, because it's the *totality* of your trades that determines whether you're "making money" or not. And 10 base hits with one monster loss means your back to square one -- if you're lucky. (Understand, my brother, I'm writing to the guy in my monitor's reflection as much as to you.)
Brett Steenbarger ("Enhancing Trader Performance" Wiley 2007) has a great little video over at Trader's Library (you can eBay it for <$20) that describes a framework we make to split ourselves off from actions/behaviors we *know* to be rotten. Holding bad trades would certainly qualify. The thing he focuses on is to identify the trigger, and then derail it.
For me (think I speak from experience?), the solution was two-fold:
1) Realize that I no longer focused on dollar return in a trade, but simply that the trade went positive.
2) Being thus "married" to a 100% or 19 in 20 win record, I took a bath in "the one that got away". FOOL.
If good trades are "like picking dropped change up off the ground" or like the lion who goes after not the biggest antelope, but "the newborn, the lame, the *lame* newborn[!]", then sitting around sweating for a trade gone awry to come back IS NOT GOOD TRADING. Nor is it "making money". It is losing.
So:
-- Don't lose.
-- GET OUT of losers.
-- Take note of your trades: start a diary, and enter your thoughts when a trade turns; note when you first think "Ooops"; note when you think "Damn! Shoulda gotten out then, too!"
-- Show this diary to your wife. Explain the losers to her.
-- Section off your account to where you can only trade close to an account-closing level -- to where you can't *afford* to lose, else you stop trading entirely.
Confronting your trigger behavior, diagramming your exit failures, and (en)forcing [failure] limits should each lend a hand.
But the bottom line is to realize that you are NOT "good at making money" but are only good at jumping into a trade. You don't *care* enough about the lost money. Get a mechanism around that one so that you realize that good trading is *finishing* with a basketfull, not an empty basket. Think: "WHAT WOULD I ADVISE SOMEONE ELSE TO DO?"
Very best wishes, brother.
TMc in Indy, IN