I do have some issues with the title. I don't believe we are designed or meant to be any certain way. We are simply a product of evolution which has no intent or design. That being said, I do understand that happiness is a state of mind, and there will be times in our lives we will feel happy, and other times that we do not.
The portion of the title urging us to stop trying makes no sense to me. If enjoying life with someone makes you happy, why would you stop doing that? That's nonsense.
I will say that lasting happiness belongs to those who are easily contented. So the simple way to feel happier is to want less and expect less. Every day reflect on all the things you have to be thankful for, and learn to appreciate the simple things in life. It seems the disturbers of happiness are our desires, our griefs, and our fears. Learning to manage them is a valuable life skill, and can go a long way to experiencing a more consistent level of happiness.