Even if people end up doing awful things, you can empathize with their motives when you know them. When you get to know the person, you can understand why they make those choices, even if they're bad. And oftentimes people do have good drives that are sympathetic and can even be seen as selfless and good-hearted.
If you're in a relationship and you want to make it work, you have to be a little selfless at times.
To me love is passionate, it is honest, and it is selfless.