One of the hardest things I've experienced is seeing the one you love so angry and upset and knowing you were part of the reason to cause him or her to be like that. It doesn't even have to be on purpose. You could think the other person is fine but something could have happened so they are more sensitive. Things you say that are normally okay hurt them, and in doing so, ends up hurting you.
When you love someone so much, you want them to be smiling and be happy as much as possible. Just sensing they are in pain or seeing them hurt, brings tears to my eyes and a heaviness in my heart. The hardest type of courage and strength stems from overcoming that feeling. Overcoming the want to cry, that sinking feeling, so you can be strong and cheer them up. Why? Because if they're already hurting, seeing you hurt will just exacerbate the situation. So you hold it back... let it out later, somewhere else. Or even better, it might be gone then.
Distract yourself. Distract that person you love so much. They'll forget their troubles. They will smile, making you smile.
That, I believe, is genuine love.