Both of these are legitimate issues of stress. Even if they seem contradictory.
Everyone should like some measure of change...because we eventually get bored with something.
I like to think of it in terms of employment.
The idea of getting a promotion or taking a new job IS stressful. So many unknowns.
However, the idea of staying in the same position for 20+ years is just as stressful. No hope of better pay, new opportunities, being stuck in a rut that bores you to tears.
When most people (NT and AS) choose to move on deals with comfort levels. Typically, depending on how much I "enjoy" where I'm at, after a couple of years, I'm more vigorously looking for something "better" than where I'm at because I want to make more money, get better benefits, etc. I also fear that staying in the same job too long may indicate I can't do anything better.