What makes us happy?

Now,the title is sure cliche beyond doubt,but thats the question that keeps me haunting a lot of times.Once someone had told me that I m a sad soul ...I really dont know why I remember such good-for-nothing statements for so long..!! But it surely set me on do some soul searching , to find out why I appear sad to many people. As I dont seem to get the answer to this question directly, I'll try the indirect way. So here it goes - What makes people happy ?I ve observed there people are happy because they got new clothes,did some shopping,saw new movies,got new bike etc and what not..And now I m coming to the point all the above mentioned dont make me so much happy.So when all the people relish in the happiness of such things which are achievable without much effort, I keep sulking about things I did not get and things I couldnt do.
So , If someone tells me to recall happy moments in my life I would say

i) When I was delightfully surprised with my SSC result

ii) When I got a scholarship which I never remotely hoped to get.

ii)When I got my first job
and so on....
Having said all this, I would ask myself, for how long could this events keep me happy? I must admit,although to my chagrin ; not long enough. I mean you are probably happy for a day or a week or a month at the most.So,the things that should make me feel good about myself didn't last for more than a month while the ones I sulk about last for years together..!! How apalling is that..!!
So bad things happening to me have a immense power of keeping me sad and depressed ,but at the same time the happy moments that have the power to conquer them are not allowed to remain for long by none other than me.I guess now I m coming close to the answer,but will stop here itself before things get messy and complicated..!! :-)

P.S :Sorry..!! two posts on the same day..coz wont be getting time to publish regularly .. :-)