I almost never get discouraged when I lose. Usually I start giggling, I think fighting games are fun, and playing against people who are better than you is a good way to get better. The only time I ever get annoyed is when the reason I lost was because I repeatedly failed to nail a combo I should have, because this implies a personal failure on my part.
I know this guy who is a bit of a dick about losing who I netplay occasionally. See, he has quite a bit more experience than me, and I've been playing against him since I just started, which I think was about a month ago. I think the problem is that I played against him a lot and I adapt at a reasonable pace, so I started improving rapidly and he wasn't expecting me to start beating him in a third of the games we play together so quickly. Whenever I win, I watch in amusement as the cursor immediately drops down to "once again" after the fact.