I'm not certain which is grammatically correct, but I would say "might."

"May" also seems correct, but it sounds more formal to me and I wouldn't use it.

I could be wrong. Hope this helped.

This is an Answer Board question, not a Discussion question, but I’d say „might.“. Might is the subjunctive (or I think it’s called in English conjunctive) mode which expresses the unreal, or what is possible, but will not necessarily happen. May techically means „to be allowed to“ but it’s meaning has been so watered down that’s it’s used in a lot of variable ways. You’d sound fine saying „you may trip“ but that’s the active voice. Might throws more the sense of “possibly but not necessarily“ in the sentence, which makes it a better choice, because that’s really what you are saying. You’d get away saying „May“ however. 

Yup Farid, it means slip or stumble in this sentence =)