Life is too long when one is not enjoying now. You recall when I was not and wished to terminate it. Your skill–and trickery, my darling, and don't blush–changed that and again I savor now. But perhaps I have never told you that I approached even my first rejuvenation with misgivings, afraid that it would make my body young without making my spirit young again–and don't bother to tell me that 'spirit' is a null word; I know that it is undefinable . . but it means something to me.

But here is still more of the truth and all I'll try to say about it. Although long-life can be a burden, mostly it is a blessing. It gives me time enough to learn, time enough to think, time enough not to hurry, time enough for love."

From "Time Enough for Love" by Robert A Heinlein.