Love is both an action and a feeling. The action of love generates a blissful feeling called by the same name. When the action stops, the blissful feeling is replaced with pain. There is a similar feeling called lust which may be confused with love. You need to decipher between the two in order to have a healthy heart. Every person is capable of great love (and its opposite, fear, which generates all painful emotions such as hate, greed and jealousy).
While there are many different ways to define love and there are many different ways to love someone (or even yourself), here is a general guide to loving.