I know exactly how you feel.  It is what I fear the most.  My daughter is 12-1/2 and what we have done is to make her more responsible for her meds now so that when that time comes, she will be used to doing this daily and hopefully won't do something stupid like not taking them.  She understands why she takes them and when to increase, although she never increases her meds at this point on her own.  I don't know that there is anything else we as parents can do.