brickmann, coates, and janoff bulman asked paralyzed people about their happiness before and after they got paralyzed...most answered that they were no big difference ...its from 1978 but i think still valid
in generell enviroment plays a factor but its not everything. the way your rewardsystem, your dopamin system works and which side of your brain is more dominant (right or left) is probably as important (im not kidding people who had a stroke which mostly affected the left side got highly depressed while people with right cerebral lesions often become euphoric even though they are highly disabled after incident) as the environment
eg we have this guy
and i garantuee you we have also a healthy, rich, good looking trustfund kid who offed himself on the other side