Might reflects possibility. We use this modal if we are unsure that something will or will not happen.
For example, if you’re unsure of your plans for the evening, you could say: I might go out, but I’m not sure.
If you’re unsure if you’d like to go out, you could also say: I might not go tonight, we’ll see.
Whether you use the affirmative or negative form is really up to you and how you want to spin your sentence. Do you want to emphasize that you might NOT do something (you’re leaning towards no)? Or that you might do something (you’re leaning towards yes)?
Give it a try, and don’t forget, if you have questions, give us a shout!