Do humans deserve happiness? An amazing thought, truly. And to answer your question - I think exactly the same. Not only that people don't deserve happiness, they don't deserve anything. Here's why:
Happiness isn't something a human can deserve. It exists in order to establish balance.
People might start feeling happy because of various reasons - relationships, jobs, achievements/success,... But as mentioned, when they see others being happy, too, it seems that it awakens anger and jealousy in them, making them feel sad again.
E.g. - A man has been unhappy for years. He didn't have any close relationships and owned a very small amount of money. Suddenly, he was offered a job in an office. That made him happy, but most importantly - he was now happy with himself. He thought he achieved something, it made him believe his value was high (or higher than he thought). However, when he entered the office, he saw how many other people got the job as well. Abruptly, this high value he once thought he had, disapeared. He realized that what he "achieved" meant nothing since so many other people have done the same.
It is a never ending circle. Happiness and sadness balance each other as everything in our world does.