A Weight off Your Shoulders:

You can say a weight is off your shoulders if you no longer have to worry about something or deal with something difficult.

Thanks so much for agreeing to take care of Snoopy while I'm away. It's a weight off my shoulders knowing that a real dog lover will be looking after her.

I think it was a real weight off Cathy's shoulders when you offered to take care of the arrangements. She's got so much else to deal with at the moment.