OK, take a few deep breaths and relax. Most of us Mooncuppers have been where you are, we got it out, and ended up complete converts and fans of the Mooncup.
Things that I have found help me:
The more relaxed you are, the easier it all it.
Sitting on the loo, rather than actively squatting, allows you to physically relax your muscles and reach in without having to ballance as well.
You don't need to break the seal immediately (I never do). If you reach in with your middle finger - ie the longest one - bear down, and simultaneously breathe out, the M will descend far enough for you to grip it between finger and thumb.
Twirl it gently as you pull it towards the outside. This often breaks the suction. At the very least it will avoid the sink-plunger sensation, while allowing you to get closer to the rim.
Remember to breathe out with a loose jaw and soft mouth. That will help prevent you tensing up.
If sitting on the loo doesn't work for you, try lying on your back with a cushion under your hips. Yes, 'that' position .
If you're still struggling, go have a bath/glass of wine/bar of chocolate, whatever helps to relax you and try again later.
It will be all right, promise.