One of the great things about first person POV is its immediacy. First person takes the reader right into a character's brain, right into the middle of whatever they're experiencing. But sometimes, the very thing that's supposed to pull us into the scene, takes us out.
I think it's easy when writing in first person, to slip into a rhythm where, particularly when we're describing action we're constantly making "I" statements like, I feel, I see, I hear.
These "I" statements can be distancing to your reader. (Not to mention they get pretty tedious when almost every sentence in a paragraph starts out with I.)
Think about it. When I read:
Cold water trickles down my back.
I shiver because I feel cold water trickling down my own back. It's subliminal. We think to ourselves this way, so when reading a sentence that is something we would say in our own mind, we react as if it's happening to us.
Now, when I read:
I feel cold water trickle down my back.
I am forced to take a step back. I picture the narrator shivering as she feels the cold water. Because it's her experience. She's telling me what's happening and I have to picture it. So suddenly, I am sympathetic, and I'm still interested to know what happens next, but I'm not right there in the moment with her.
See the difference?
Of course there are times when you want to create that bit of distance, or an I statement is really the only way to drive your point home, but don't forget to pull your reader as close to the action as possible whenever you can.