Nicholas Rush in a sentence would be: "An arrogant man who believes he knows more than everyone else on the Destiny, except, he may be right... if one doesn't consider Eli."  Rush knows he's important to the Destiny and he knows that he knows things that everyone else doesn't know, and those things make him important.  However, he doesn't tend to share these things with people, and uses them to manipulate the crew and everyone else into doing what he wants because he believes that his course of action is the best, and if they knew everything, first they wouldn't understand.  Second, they wouldn't be smart enough to realize why his course of action is the best, as he would believe they wouldn't weigh things as they should, letting their ignorance or their emotions cloud their judgement.  Rush's ego, therefore is fairly inflated, though lately its been more deflated as he realizes that Eli Wallace is indeed smarter than him, and he's coming to terms with that. 

Rush is a very strong willed person, who has gone through a ton of trauma, from his wife's death to being captured by aliens to being tortured by the Lucien Alliance.  However, he still pushes on.  It could be said it is unhealthy, how he deals with these things, as he tends to keep to himself.  He doesn't have many on the Destiny that he feels comfortable enough to open up to, and so he bottles these traumas up inside of him, causing occasional breakdowns.  The stress of the Destiny is major and doesn't help at all, and yet its almost as if he liked the stress, the danger of the Destiny because it lets him be distracted from the things he doesn't want to think about. 

However, Rush loves to be listened to and hates when they don't trust him, even though he knows his own history and why they wouldn't trust him.  Except he knows in that history, if they just listened to him they would be just fine.  And that is what frustrates him.  Their not believing him is precisely why he keeps things from the others to get them to do things his way.  Their not believing him in the past hasn't made them learn to trust him.  Yes, okay, he's been wrong before, but the times they didn't trust him and he was right far outweighed the times he was wrong.  This trust plays into the fact he likes control, because without control, then he feels like he loses control of his life and that is a scary thing to him.  He feels like he can't trust others, he can't let go of the reigns or they will all die.  Leaving things to fate, or if something is out of his hands, it's Gloria all over again, and he hates that. 

Nicholas Rush was a professor at a college where he taught Physics.  He'd always been a brilliant mind, and not very good in social situations.  And yet, he met a young woman named Gloria and not long after they were married.  However, fate had a different idea for them.  Despite Rush's love for his wife, when she needed him, he wasn't around too often.  When she had terminal cancer, she tried to be with her, but he also tended to shut himself up because he didn't know how to deal with it.  He didn't know how to deal with Gloria dying.  And then she died and he joined the Stargate program. 

He always felt guilty over the fact that he didn't spend all of his time with Gloria, and regrets it to this day, even causing a whole vision trip from the Destiny's control chair to reenact the whole situation causing him to sour afterwards for awhile while he tried to get over the whole situation again.  While at Stargate, Nicholas Rush became an expert on the Ancients, their systems, and paired with his physics knowledge, became the lead scientist on Icarus Base, where he was working on a terribly difficult situation trying to unlock the Ninth Chevron, which with the help of Eli Wallace, they were able to do, leaving them stranded on the Destiny together.