No matter how much you give to your work, your manager would move on to finding a replacement once you move on.

This does not mean they are brutal. This simply means they want to get their work done. And they are right.

This also does not mean that they don’t care about you. They do. More than you could think. However, that does not mean they stop caring about work once you move on.

Work is important. Very important. But no matter how indispensable you are, you will be replaced in your absence.
However, it is not the same with your family and friends. They love you. And they cannot replace you with anyone. Anyone. Ever.

The wisdom of falling in love, then, eventually boils down to spening time with your family and friends more often. They are the places you are truly irreplaceable.