Well this is a very good discussion question.
I find it seasonal. I think like any happy marriage, there are times when we just dont enjoy our lives as much other times, when we do very much. Both, single abd married, take effort and prayer to remain content, imho. I think the key is making Him, our Lord and Savior, the desire of our hearts, then no matter the circumstances or the state of being, everything else is just bonus.
So while I have seasons of ache, restlessness or just feeling like I am longing for something or someone, leaving me feeling all a lonely, lol, I know the problem isn't in the situation only, but in my need to find sufficiency in Him, alone.