Guys does this happen to you?

Whenever I talk to girls about my achievements like winning a game of kickboxing,catching a bad guy who tried to break in in the next door I really get hard. What could it be? Specially when the girls says Wow...you are a hero etc. I really can't bear and get a hard on which lasts for a long time during the course of our conversation. The other thing for which I get hard is when talking about underprivileged guys like laborers etc. to girls who work with me. They pity them and both me and the girl talk about how lucky we are to work for a good firm and it actually is y for me and then again I get it!!!