A baby is crying. She is crying for milk, she is hungry.
The young couple quickly prepare the milk for her and feed her. She stops crying and drinks her milk. She smiles at her mom and waves her hands happily.
A baby know what she wants and asks for it. Therefore, she gets what she asks for. And she becomes happy for getting she wants.
We adults frustrate because we are not clear for what we want.
Once we know what we want, we will ask for that, then we have a good chance we will get it, which makes us fulfilled and happy.
Find what you want at the first place.