Happiness is a state of mind that you have a lot of control over. When your vision of the world does not match reality you are bound to be disappointed or frustrated, which creates unhappiness. That kind of feedback means that you have to change your perspective.
Some happiness comes from your own actions towards others, and from the actions of others towards you. Again, you have some control over those relationships. That being said, we are all different, and our opinions do not always align. Some compromises can be made, depending on what each person values most.
Speaking of values, happiness doesn't necessarily come from meeting all of your wants and needs, (provided you have enough to live decently). Most people are unhappy because of ambition, greed, trying to control or manipulate others, jealousy, etc. Cultivating a state of mind where your opinion of yourself is based on truth is a nice way to constantly improve and achieve long term fulfillment.
That being said, most people aren't willing to look at themselves in the mirror with absolute honesty, accept what they aren't good at, and do something about it if it's important to them. People lie to themselves, to others, and aren't willing to accept being told the truth about their own behaviors and actions. After all, we perceive things differently. Morality, good and evil can be debated forever. But actions (and inactions) have consequences: "you reap what you sow".
Happiness is a skill, which must be learned and practiced. Knowing the depths of depression, and considering where I come from, I can say with confidence that I can be happy no matter what. It's a strength but also a curse. Once you achieve mastery of that state, it becomes difficult to understand others who haven't graduated and still act selfishly in most circumstances, always going for the easy path, the quick fix, the instant gratification. You expect better, you see the alternatives, and you are shocked to see how much people are ruled by their emotions.
Emotions are important, but making good decisions over a long period of time will have a bigger impact on your overall happiness than trying to satisfy your pulsions, no matter the consequences. I just wish, more people were conscious of that. It's probable that a lot of the "evil" that exist in the world is the result of a lack of growth, knowledge and experiences. Maybe if people knew, and could, they would do better for their own sake and that of others.
Smoking, alcohol, drugs, sex, food, gambling, gaming... etc. People are often hooked on those things that are detrimental to them, and yet don't try to change. Most of the time, they enjoy the feeling of being around those who are in control, as if it was a substitute for the efforts they must do to achieve the results they want. Qutting an addiction can be really difficult, especially when it's used to escape a harsh reality. Sometimes, only outside help can reverse the process. Love and care is key.
That is something I struggle with a lot. When you have the ability to see faults and improvements everywhere, it's hard to be satisfied with something that is clearly suboptimum. Perfectionism gives you the strength to persevere towards a difficult goal, and that creates growth. However, it not only affects your ability to perform (due to the exponential raising cost), but also the pressure you put on others to perform at the same level as you.
The only way to beat it is to accept imperfection. This doesn't mean to stop trying your best, it means doing your best within a time limit, and go for less optimal options if the result is still good enough.
Seeing others make mistakes (that impact you), in job relationships, dating, or even gaming automatically triggers some level of annoyance. It can even become anger, and when you'll try to voice your concerns, others won't care or understand (why you're upset) and feel offended by your criticism.
It's a mental state of feeling powerless to do things that could improve your happiness. This can be forced upon children who receive a bad education. For example, an artist who is not allowed to express himself, can feel this way. Same thing for a young adult who is denied higher education (or opportunities), despite his talent.
The only thing to do is quit to this environment that doesn't suit you. However, giving up all the time (while blaming others) is a symptom that you haven't learned a way to adapt and compromise.
To combat this, one has to realize that anything is possible. Even an event with a 1% probability will happen given enough tries. It's this hope, that can make people addicted to gambling, so one must be careful about wishful thinking. That being said, hope is also what allows us to keep going on day after day. Just be mindful of what you are hoping for.