It's odd, but whenever I write in first person, I write more as how I'd react to the situation, rather than how the character would react. There are some differences, but I can see the similarities glaring at me, and I do not like it. Now, what I want to know is how you overcome this problem.
You could of course write in third person, as an exercise-- this, because I think you're putting yourself, or your grabbing your character into his/your shoes. Try and distant the character from yourself a bit, and get into the character's mind. Since you have adressed this as a problem, I would guess you've tried to eliminate it prior to this thread. So maybe, you can also put 'your self' into the form of a secondary character; focus what you'd do on that one character instead. In retrospect however, sometimes a few similarities of a real person(you included) add more to the realness of said character. It's much easier to characterize with a literal example than it is to make up your own. But also keep in mind, you might want to keep the similarities between you and your character to a few quirks or so.
Think of a real life friend who has characteristics similar to your fictional person. How would you expect your "friend" to react in a situation?
that's another good reason for not writing first person fiction!... but if you insist, you need to learn to separate your self from your characters and the story... become the character, instead of letting the character become you...
