When it comes to being in love, how do you know?

It is when you cannot bear to see her sad, or hurting. 

It is when you know that no one else would give the best care the way you do, 

because with you, she feels that she is the most important part of your life, that she is your life. 

No one else. Nothing else. 

You cannot live without your heart, and she has your heart in her loving hands. You've given your heart to her in exchange of  yours, with a hopeful promise of forever.