I find the key with being happy with inter-personal relationships or just with life in general is being happy with yourself and not defining your self-worth based on whether you're in a relationship or not.
I'm 31, single for over a year, and it doesn't bother me at all. I honestly simply don't care. I just visited my brother (same age) who's married to a great girl for I think six years now and has a young child. I came away from the trip thinking "wow they're all doing great, seem really happy, that's great", not "oh no, I'm single, no real prospects for changing that right now, no children, woe is me." I would like to be in a great relationship with a great girl, but I don't think that's something you can or should have to seek out. It should come more or less naturally out of the normal dynamics of your life. Fuck going to the ends of the earth or stressing out on getting some chick to like you, convincing someone who's essentially a stranger that you're worth a damn, etc. I'd rather spend my time socializing with and visiting friends and family, working on a job that I love, things that make me happy and add to my life rather than subtract from it, like many relationships often do, and yet people cling to them because they lack self-confidence and define their self-worth based on what one other person thinks of them romantically.
Similarly I'm not a big believer in "working" on a relationship. If you have to work on it constantly you should probably take a step back and reflect on why you're in it in the first place. It's not supposed to be hard.