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 I sent you
That you quickly burned
It's not the book I lent you
That you never returned

Remember, it's my heart
A 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