If you should decide you don't want to play, you can remove yourself from any group via the Your Group Members screen.

Your name will have a big red X next to it.  If you click that, you will have the option of dropping from that group.

By dropping from a group, you are only removing your connection to that group, not deleting any of your data.   You can join another group or rejoin the same.  (although we're not sure why someone would drop, then rejoin)

Also, managers (the creator) of any group can "quit" anyone in the group as they will see red Xs next to everyone in their group. Same thing applies here.   If a manager drops someone, they are removed from the group but none of their data is deleted.