Assuming you are just talking about happiness with respect to
singlehood, how happy you are as a single will depend on how strong
your desires to attachement/relationship is.
Thus,
1. If you have no desire to be attached, then you will always be
happy.
2. If you have a small desire to be attached, then you will be
happy most of the time.
3. If you have a strong desire to be attached, then you will be
unhappy most of the time.
4. If you have a very strong desire to be attached, then you
will be depress all the time.
All of us starts at level 1 (like when we are just a baby, no
attachment, but always happy), but as we grow older, our desires
will start to increase depending what kind of environment we grew
up in.
Controling ones desire for attachment is difficult. Although I
underdstand that no desire for attchement is the best , I still
have desire to get attached. 
