Depending on one's age and life experience they will define love differently.
Some people are never quite sure if a person truly loves them. This explains why you see so many hubs, articles, and blogs with the title,
"How to tell if he really loves you..."
Not everyone needs the same amount attention to feel loved. Some people are "high maintenance" and require being showered with gifts, trips, and affection in order to feel "special". Others are content with words, small deeds, honesty, consideration, and companionship.
Since "We are who we are", One person might consider themselves (showing their love) but they're with a mate whose definition of love does not match theirs. It's hard to "appreciate" a gift if it's not exactly what you wanted or what you expected. Last not but least sometimes it's the "right love" but it's coming from the "wrong person". Some people are impossible to please! :-)