What happens if my I-485 is rejected?

I recently started worrying about what happens if my I-485 is rejected. What are the next steps I can take? Can I refile my case? Or do I need to leave the US?

to Cathy:

Do you have a valid visa status? If so then you are fine. Even if your I-485 is rejected you can still stay in the US. I mean if your visa is still valid at that time.

to Cathy:

Yeah if your visa is still valid then you don't need to leave the US. As for refiling I-485, I guess it depends on the reason of denial. You might want to check with an attorney on this.