Be Careful, It's My Heart

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.