It depends why I lose.
If its because of stupid shit out of my control, like the input bug turning my uppercut into a standing 2 after landing a spear on someone that has like 10% health left, or an equally retarded "NRS" situation, I get really annoyed.
If I just got outplayed or was due to my own error, I don't get bothered much by it. If it's in a tournament I'll be pissed at myself though. I still have nightmares thinking about all the easy shit I dropped repeatedly at Final Round. Like super easy shit like a simple vortex string that I dropped 3x in a row in my first match, which was on stream making me look like a retard.
Nothing is more aggravating though than losing a close match online due to a horrendous lag spike hitting at the worst possible time, and then getting hate mail about how much I suck and how invincible the other guy is, even if he got babied the last 10 matches. Though this is just as funny as it is aggravating.