You cannot say " I have no heart to do sth." For example, Chicken soup for soul, not for hearts. 7 m8 Z2 O7 H, q1 z! ?
Your context is not very clear. So can you explain the contexts more clearly? * k5 z& Y% O9 V) N$ u; YWhy you don't want to bother the boy again?
For the first context, just say I am sorry to bother you again. & |! b; t, Q/ y" v/ R& L
For the second case, I don't think you can use hearts in this expression. You can say I am not meant to do sth...