In The Empire Strikes Back it seems like a weird choice for Yoda to live on such a lonely and remote planet, considering how social Yoda actually is. Why does he choose to live there?
There are parts of Dagobah that are "strong with the Dark Side."
After Emperor Palpatine came into power and there was a purge of the Jedi, the few Jedi remaning alive hid, hoping to be able to do something more in the future.
Because Yoda was a powerful Jedi, he hid near a source of darkness that would hide his presence so any Sith looking for him would not be able to sense his presence easily.
(Much of this comes out in Revenge of the Sith.)
Dagobah is hardly lonely. It is filled with layer upon layer of life. Perhaps all that life helps hiding Yoda's powerful force.
Yoda does not seem very social to me. He seems to be nearly 100% instructor, even during Jedi council meetings.
Also, Yoda does not fit the description of "bad ass". He can certainly kick ass, but he doesn't do it for fun or pleasure.