Cancelling your recurring donation can be done directly from your user account, and can be done at any time. Head to www.mightycause.com/login, and login with the email used when creating your recurring donation. Once you have logged in, select your user icon in the top right hand corner and choose 'Recurring Donations'
This will take you to a page that looks something like this:
Once here, choose the 'Manage' icon to the right of the recurring donation you would like to cancel. In the pop up window, choose 'End this recurring donation.'