A lot of people just forget that they're actually happy. Sadly, in the act of forgetting that you are happy, you are making yourself unhappy. If someone asks you "Are you happy?" and you find yourself trying to ascertain if you're happy or not, chances are that you forgot. It's not necessarily a bad thing. It's like leaving the stove on and forgetting about it: best case scenario is that your food is done, worst case scenario is that your house is on fire. Either way, if you don't periodically check, you just don't know.
Some people get really upset when they found out that the set of kitchen knives they just bought went on sale a week later. Or that the blender they bought was not in fact number one best blender of the year 2014. This probably sounds petty to you, but it doesn't have to be petty. I used to think that people who pursue better blenders are the same kind of people who would think that having a house and a mortgage would be the end goal of their life and the absolute thing they would need to be happy. Given that I'm currently looking to purchase a house (and, consequently, a blender) there is definitely some irony at play here. Here's my attempt at nuancing my change of opinion.
When you see people trying to increase their happiness by buying a better blender, what you're really seeing is only the topmost layer of what people think they need to be happy. The fact that they're looking for a blender can either mean that they've already ticked off from their list everything else that could possibly make them more happy than a blender, or it could mean that they're so shallow that they think they only need a blender to be happy. Or something in-between.
I think the foundation of happiness is accepting the phrase "I can be happy with anything". In order to truly accept this, I suspect that you will first have to lose everything. I honestly don't know. I've had my bad times but I've never been particularly close to this statement, which makes my foundation for happiness less-than-optimal. (Although perhaps the realization of this fact offsets the lack of depth a little). People who have this solid foundation for happiness in place will not get upset when they buy a shitty blender: they know that their foundation for happiness lies much deeper.
I know people from both sides of the spectrum. Some get really upset when some trivial thing happens in their life, which may cause them to be unhappy for weeks. Others have the most terrible things happen to them and they laugh it off. Some of my friends are, like me, transitioning from the "I can be happy with anything" mindset into the "Ok, we've established that I can be happy with anything, now where do I get a better blender?"-kind-of-mindset.
Don't forget your foundation, but don't cling too much to it either. Or else you'll never have a nice blender.