Mulder: Scully, did you ever have one of those days you wish you could rewind and start all over again from the beginning?
Scully: Yes. Frequently. But, I mean, who’s … who’s to say that if you did rewind it and start over again that it wouldn’t end up exactly the same way?
Mulder: So you think it’s all just fate? We have no free will?
Scully: No, I think that we’re free to be the people that we are - good, bad or indifferent. I think that it’s our character that determines our fate.
(Season 6, ep. 14 “Monday”)

Scully: These are tricks that the mind plays. They are ingrained cliches from a thousand different horror films. When we hear a sound, we get a chill. We see a shadow and we allow ourselves to imagine something that an otherwise rational person would discount out of hand. The whole idea of a benevolent entity fits perfectly with what I’m saying. That a spirit would materialize or return for no other purpose than to show itself is silly and ridiculous. I mean, what it really shows is how silly and ridiculous we have become in believing such things. I mean, that… That we can ignore all natural laws about the corporeal body, that we witness these spirits clad in their own shabby outfits with the same old haircuts and hairstyles never aging, never… Never in search of more comfortable surroundings - it actually ends up saying more about the living than it does about the dead. I mean, Mulder, it doesn’t take an advanced degree in psychology to understand the… the unconscious yearnings that these imaginings satisfy. You know, the longing for immortality the hope that there is something beyond this mortal coil, that we might never be long without our loved ones. I mean, these are powerful, powerful desires. I mean, they’re the very essence of what make us human. The very essence of Christmas, actually. (Season 6, ep. 6 “How the ghosts stole Christmas”)

Skinner: When I was eighteen, I, uh… I went to Vietnam. I wasn’t drafted, Mulder, I… I enlisted in the Marine Corps the day of my eighteenth birthday. I did it on a blind faith. I did it because I believed it was the right thing to do. Three weeks into my tour, a ten-year-old North Vietnamese boy walked into camp covered with grenades and I, uh… I blew his head off from a distance of ten yards. I lost my faith. Not in my country or in myself, but in everything. There was just no point to anything anymore. One night on patrol, we were, uh… caught… and everyone… everyone fell. I mean, everyone. I looked down… at my body… from outside of it. I didn’t recognize it at first. I watched the V.C. strip my uniform, take my weapon and I remained… in this thick jungle… peaceful… unafraid… watching my… my dead friends. Watching myself. In the morning, the corpsmen arrived and put me in a bodybag until… I guess they found a pulse. I woke in a Saigon hospital two weeks later. I’m afraid to look any further beyond that experience. You? You are not. Your resignation is unacceptable.
Mulder: You gave me Cancer Man’s location. You put your life in danger.
Skinner: Agent Mulder, every life, everyday is in danger. That’s just life.
(Season 2. ep. 8 “One Breath”)

“I think that you appreciate that there are extraordinary men and women and extraordinary moments when history leaps forward on the backs of these individuals, that what can be imagined can be achieved, that you must dare to dream, but that there’s no substitute for perseverance and hard work and teamwork because no one gets there alone.“ 

~ Dana Scully