Every relationship needs give and take between two people to truly be a relationship. The term "give and take" is not new. It's a simple idea that says that to have a productive and satisfying relationship you can't just do all the taking or all the giving all the time.
Unfortunately in reality many relationships are either: "You give and I'll take" or "I'll give and you take". If you are doing all the planning of dates, paying all the expenses, sharing and repairing relationships you are giving too much. If a relationship feels like too much work on your part, you feel like you're squeezing water from a stone, or the person requires a lot of nurturing to extract even a small amount of value, you're not in a "love" relationship, you are giving too much.
When your giving is taking too much out of you and threatens to destabilize your very person, then you are trying to give more than you are capable of. If you allow yourself to be drained of energy you will have less to give to a deserving man or woman and may find yourself passing up good men and women because of the experiences of your past. If you allow one or more experiences to make you cynical, then you have given more than you were capable of and it has made you less than who you were. This is giving more than you are capable of giving. To open yourself to others is often rewarding but is only as good as the value it adds to who you are.
If you are giving because your help is needed (in sickness or crisis) then simply accept the relationship for what it is. Your giving will add value to who you are but may not translate into a relationship with that person. And if your "generosity" has strings attached (like hoping you can subtly buy his/her affections) then it's really not very generous. And don't lie to yourself it's not likely to work out. You will probably end up disappointed.
One-sided relationships have a devastating effect on your self-esteem. No matter how good your self-esteem "GIVE and GIVE" relationships have their own constraints which make having productive and satisfying relationship impossible.
My people have a saying: Who you are is related to how much you give of yourself without losing sight of who you are. Giving who you are to the extent that you empty yourself onto the laps of others only makes you insignificant and "invisible" in the relationship. And when there seems to be only one person in the relationship a disequilibrium in energy distribution happens and when that energy distribution exceeds certain limits, a state of instinctual emotional "distancing" begins to happen.
It is best to minimize the possibility of regret by making sure that you choose people capable of "give and take" relationships.