The stores are filled with candy and stuffed animals for Valentines Day. The expectations set by society cause a lot of pain.
I am no expert but love is a verb. People speak of "falling in love" like it is a hole in the ground, maybe "stepping in love" describes what they are doing. One of the stupid quotes from the divorce courts is "I am not in love any more" like it is a pond, a forest or a neighborhood. There are different types or levels of love. I love my freinds and my country in a much different way than I love my wife.
Unconditional love is a great concept and is easier to apply to your kids. Realationships between lovers are WAY more complicated. Infidelity, physical and psychological abuse are examples of behavior that would warrent terminating the relationship.
Love is a verb; actions, thoughts and words. Feelings follow actions. This is where the "unconditional love" concept and real life clash. If your lover does not recipricate, that is a problem. That does not mean that an instant tit for tat response is required or even desired. "Keeping a list" is a concept that can destroy relationships. If the list is a fairness scale then any imbalance causes problems. An alternate list is how/why I love you, or what I like about you and that can strengthen the bonds. Doing stuff for your partner without expecting anything in return is love.
One of the misconceptions of a successful marriage is that it is a 50/50 relationship. Both partners need to be in 100%. Trying to make sure you get your fair share and keeping score ends in resentment. Trying to give your best and rooting for your partner is a road to fullfilment.