Be Careful, It's My Heart lyrics

Be careful, it's my heart, it's not my watch you're holding, it's my heart.
It's not the note that I sent you that you quickly burn,
It's not a book I lent you that you never return.
Remember, it's my heart,. the heart with which so willingly I part
It's yours to take, to keep or break, but please, before you start,
Be careful, it's my heart.

Submitted by Guest

What do you think is the meaning of Be Careful, It's My Heart by Frank Sinatra?