The thought of letting your younger daughter go when it's time for her to move into the next phase of her life is obviously bringing up a lot of grief for you, and that's completely understandable. Maybe use this time to find a project or interest you feel passionate about to lessen the sting. I don't mean to sound trite but having something else to focus on really helps. It's a new phase of life for you too and you know your daughter would want you to embrace it. Sounds like you could make a great foster carer if that's something that interests you.