I think, too, that not everybody has to achieve the same level of 'happiness'. I suffered from major depression for years (used various medications, had therapy, etc.). I seem to be back to 'normal', for some time now. (I still take an anti-depressant, but it's for anxiety issues.)
On the other hand, I'm not running around smiling all the time. My husband nearly died in 2004 (medical problems), and we went through long periods of medical care, financial troubles (which we're still experiencing), and just all-around difficulties. We both ended up unemployed when his medical problems were at their worst. That was hardly anything to be 'happy' about. And now I'm working two jobs to pay down some of the credit card debt that we accumulated during that time. I hate working two jobs. My husband works different shifts, so we rarely get to see each other. I'm not happy about that either. I don't get enough sleep, I never get a day off, I don't get to see my husband much at all, I have no time to myself to pursue my own interests/needs, etc. I'm hardly bouncing off the wall with joy.
On the other hand, I don't think I'm depressed, in the clinical sense. My life is just not a 'happy' one, but that's not the same thing as being depressed. The feelings I experience now are just frustration and disappointment at my lief situation, but I don't feel depressed per se (and I know what that feels like).
So, other people might think that you're still sort of 'low', but you can feel that way without being clinically depressed, I think. The important thing is how *you* feel, not how other people perceive your feelings. If you think you might be depressed, though, then you should seek medical/professional care.
I will never be one of those happy-boppy people who jumps out of bed in the morning, just bursting with happiness, and feeling high on life. If other people feel that way, then good for them. But it's not me. And I don't think that means there's anything wrong with me - we're just all wired differently.
Right now, my only attempt at achieving a happier attitude is just to ake a stoic attitude - more one of resignation than anything else. I realize that there are certain things about my life that I can't change right now, and I just have learned to cope with that. That's not the usualy key to happiness, but it works for me right now.