Hi, Sadfella:
I remember you!
You are at your nadir right now (in the grand scheme of things). No matter what you do, no matter where you go, you will find some association (however tenuous) with your former partner. That will go on for awhile. You have to mourn your loss. You can't be with someone for as long as you were and not feel acute pain for some period of time.
It's terribly scary being on your own again. If you go back to your first set of posts I prolly told you about the ending with my first True Love.
How to find a smile? How about trying to find something good every day. It doesn't have to be anything good, it could be seeing the sun, enjoying elevenses, seeing a good movie, talking to a friend you haven't seen in awhile, just something small. If you can appreciate the smallest bit of harmony in the cacophony around you, you are on the way to healing. Everything comes in small steps and it sounds like you've made quite a bit of progress.
It's very difficult to look ahead when you're going through healing--sometimes you have to look back to see how far you've come. Could you possibly set yourself an easy goal to look forward to--even something silly will do. You'd be surprised how even accomplishing the smallest of things can be such a lift.
One suggestion--make sure you get enough sunlight. Doesn't that sound crazy? There's a medical condition called "Seasonal Affective Disorder". It's depression that is related to the lack of sunlight. As the name happens during the winter. The farther north one travels the higher percentage of the population is affected. I have it (I lived in the Chicago area for the first 30 years of my life and didn't know I had it). There is something called "Light Therapy" that might help. Part of your unhappiness could be because of the time of year.
You also might want to talk to a mental health professional for a med to take to help you stabilize your mood (I also suffer from depression and am slightly bipolar). You don't have to be on the med forever but it might help keep the bad moods from being too black.
Just as littlemissdreams said, you will learn how to be happy again. It just takes time (God, give me patience and give it to me NOW!).
Feel free to pm me if you need a sympathetic ear.
Good luck and please keep posting.