I had just opened up to a good friend of mine about how, after 10+ years of intractable treatment-resistant depression, I was completely exhausted and really did not want to be alive anymore. At the time, I had kind of accepted that things would eventually get better, but I thought that it would be years until my life was what I wanted/needed it to be, and I just felt incredibly frustrated at everyone telling me to "wait it out".
Instead of giving lame advice, he asked me more about my plans, and it came out that the only thing that's ever kept me going is a drive to contribute something meaningful to humanity, and I just couldn't stand the idea of giving up and essentially leaving the world a little worse off. That's when he busted out this one:
"You know, I think it's almost tragically beautiful that you keep putting yourself through this just for the sake of other people. I know it's hard to believe it'll ever be worth 15 years of suffering, but once you're on the other side of it I think you'll see what an incredible person that makes you."
It still makes me tear up every time I think about it. It was one of the most important things anyone's said to encourage me, and it helped get me through some of my worst times. Thankfully, it was only about a year after that that I finally found a treatment that worked. No updates yet on the giant ego I'm supposed to be growing, though ;)