So... this happend...

https://www.youtube.com/watch?v=G4aJ...ature=youtu.be

i heelhooked myself and tore my meniscus, but all my ligaments seem to be fine according to my doctor.

I probably won't be back on the mat for another month or two.

any advise on how to keep yourself fit and avoiding further injuries? my biggest fear right now is that it might happen again...

Ouch! Heal well and fast.

Well I guess you could have released the closed guard as dude pulled mount but in all fairness it was unlucky as hell. Just one of this freak occurances.
All the best with the recovery.