Why Are Some People Naturally Happy And Others Even If They Have A Positive Attitude Are Always Miserable?

Probably just that person’s personality.
It also could have a lot to do with the environment that they were brought up in.

People get happy and they get upset. It’s called emotions. And by the way, don’t automatically assume everyone is one way or the other. That’s very ignorant.

They follow these life rules:
Smile and be pleasant to those around you. Exude a positive attitude, and don’t be a complainer. People are more likely to perceive you as lovable if they enjoy being in your company. Pay attention to your personal appearance. Taking care to be presentable tells people that you consider yourself worthy to take good care of yourself in all ways, and that will translate into them having the same opinion of you. Take pride in your accomplishments and realize that you have something to offer to those around you. Do your fair share of the work when a project needs to be accomplished and you’ll be loved for making it easier on everyone else involved. Give of yourself. Recognize when a friend needs help, whether it’s just an ear to listen, or if she needs someone to watch her children for her. Do something nice for someone “just because.” Volunteer your time to charities that are meaningful to you. Be happy and optimistic. No matter your circumstances, you can choose to focus on the good, or focus on the bad. People are going to think of you as lovable if you manage to be pleasant despite your adversities.