Being "happy" is a very relative term too. Sometimes we have visions of getting sober as all rainbows and unicorns and that our lives will magically transform overnight. Unfortunately life itself has it's ups and downs, so some days we just don't feel happy no matter what we do. Having said that, as you get some sober time under your belt you have a much better chance of dealing with all the things that you will confront, good or bad.
And as others have mentioned, it simply takes time for your body and mind to heal from the abuse of using/drinking. As addicts we tend to seek instant gratification, but that's what got us into trouble in the first place.