This could be very pessemistic and distorted, but I don't think happiness lasts. I think that's pretty much the way it is for everyone. Happiness comes and goes. Ever illusive. I think what you can hold unto is peace and joy. Joy is different than happiness. It's deep, deep down. It's not quite as bubbly, it's more of a quiet contentment. I don't know. Just my two cents worth.
I hope you find happiness and hold on to what you have.