One Good Friend and One Good Enemy
That seems to be the basic requirement to stay cheerful. Somebody to cater for all your moods. (Most creeds and r*l*g**ns know this, and offer you a ready made Friend and Enemy figure - but you can easily come up with your own candidates. They don't even need to be people - e.g. you can pick a wrong that need righting for your Enemy.
The big mistake is to try and cast the same person in both roles (typically a husband or wife...

)
Cheers,
Chris
Additional Friends and Enemies still welcome....