It is not just luck. My observation has been that really really happy marriages have two selfless people in it. It is not luck to choose to be selfless yourself. It takes a lot of work, and is not fun all the time. I congratulate people for their success, I do not consider them lucky. (Even if I have not found the keys to success myself)
Absolutely. One can be honest with themselves and strive to work on being selfless. The real trick is, however, meeting that other selfless person to share it with.