The act of loving someone for who they are, faults and all. Loving someone fully takes courage and stamina, especially if there is a lot of work to be done. Whether it lasts or not, you still love that person for what they meant to you. Even if both have moved on. Even if it was only one-sided, it doesn't take away from the real emotion that was felt for that person.
When you love someone, it never goes away, it only fades in intensity.
