Why have troubles and worries

And those great philosophers and psychologist thought that they understood the human mind /emotion or shall we say humans...
is it so? Then tell me sir, why is that inspite all human beings trying to be happy why is that they are surrounded by worries ?
They are happy in a relationship but have worries about the future.. they are very happy having a good life but then they worry over all things which many of the times are beyond their control..
parents worry about their kids first for education, then their behavior in teens, then their college, job, marriage, children's children.... why don't you just take a break from routine and be happy for the moment...things will fall together whether you worry or not..I am very happy and content with my life and i do not like any deviation from happiness to worries...I dont worry about me and not about others...Its a state of mind which i really dont want to deal..Does any other person wants to? I guess no..Then why create worries in your life and then in others....