Personal investment

So I was thinking about personal investments.  Not monetary mind you, but investments we make in other people.  Like the investment spouses have made in each other -- .monogamy, fidelity (not the same thing), bearing children, time (years...), raising children, cooking meals, developing common tastes, accepting in-laws, providing a home, an income, sharing a bedroom,... all these things.  

Or the investment friends make in each other.  Not as deep of investments maybe, but still investments -- trust, contact, empathy, lending an ear or a shoulder, a joke, favors, time (again), maybe something borrowed, or maybe just a shared drink or dessert. 

All these things are investments we make, and I think we expect -- need? --  to yield a return.  Every good friend has made an investment me, and me in them.  So, we owe each other something, right? At least an even return... So the same things... caring, the lending of an ear or a shoulder, fidelity (again), "having my back", wanting to make each other laugh.  The same things.

And how empty (angry? foolish?) we feel when the return of a personal investment goes south -- especially when to zero.   Or how a relationship or friendship can get bogged down if one feels that their investment isn't yielding an even return -- isn't deserving of a return!  That has to be big part of the hurt when relationships go wrong.  "I invested in you.... and what did I get out of it?"   You weren't there for me?  You cheated on me?? You lied to me?  I didn't invest in that!  (And what else could I -- should I -- have invested in?  The time I gave you is gone.)

But fine.  So then... is love an investment?  Or is it a gift?  Better yet, an unconditional gift??  Because if love is an unconditional gift, then it doesn't ask for, or need, a return...