If your mentoring program has elected to use My Match, you can mark your profile as unavailable in My Match should you wish to do so.
To do so, log into the Mentorloop platform, and then navigate to the bottom left hand side - at the lower part of the black sidebar - you'll see links saying "Profile" and "Settings". Click Settings, and there you'll see the Available / Unavailable status buttons. Click Unavailable, and you're on your way.
If you set yourself to Unavailable, any pending requests can still be accepted or declined by the respondent.