Most events will allow you to self cancel prior to the event.  Some may not if they involve payments, site reservations, etc.

If you can't make an event, you can try self cancelling by following these steps:

• login
• click on "View profile" (upper right corner after you login)
• click on the "My event registrations" link
• select the event to cancel
• click on the "Already registered" link
• if self cancellations are allowed, click on the "Cancel registration" button

If self cancellations are not allowed, contact the Trip Leader named in the event details

Your cancellation may allow others on a wait list to attend