If you realize you have it, their is a procedure to work through your instruments to get yourself reoriented....its a matter of trusting what the instruments tell you as opposed to your mind and body. Sometimes a good ATC can help.How do you deal with it when flying alone? Didn't the pitcher Roy Holiday crash his experimental plane and died because of getting disoriented? Now I think they found stuff in his system. Not saying that caused anything.
If you don't realize you are experiencing it......the results are not good. Supposedly this is the reason for over 90% of crashes resulting from pilot error.
Don't know about the Holiday crash, but the JFK Jr. and the Buddy Holly crash were attributed to SD.