If you are a member of a Google Group or Collaborative Inbox that you don't need to access, you can remove yourself from the group. However, you will not be able to rejoin the group yourself - you will need to be added back into the group by a manager in the group.
To remove yourself from a group:
In the main Google Groups screen, position the mouse over the group you wish to leave
Click on the ellipses to show more options
Choose Leave Group