S.T.
it's hard for me to be helpful here, because my personality and parenting style are on the opposite end of the spectrum<G>.
can you pick your battles? rather than micromanaging so many things, maybe pick one or two MUSTS and force yourself to let the rest go?
at 16 your son is too old for a bedtime. tiredness the next day is a good natural consequence for staying up too late. so is a poor grade for not getting schoolwork done. sit down with HIM and ask him where he thinks he needs some helpful reminders and where he wants you to back off. it might surprise you.
your daughter might just be a lone wolf. nothing wrong with that. if she's friendly with the girls at school but prefers not to reach out, she's may just genuinely need a lot of solitary recharge-the-batteries time. most 14 year olds do want to be out with friends, but that doesn't mean that every single one should or must.
you can't force relaxation and you can't make yourself not worry. but you can make yourself butt out. if you are anxious even while you are intervening a lot, it's not as if your actions are alleviating the stress, are they? you CAN force yourself to stay more hands off.
and if it's really bothering you, you can always discuss your concerns with your children WITHOUT taking action. just make them aware of what's bothering you, and then let them do something or not, without insistence from you. that way you have expressed yourself, but are letting them make choices like the adults-in-training they are.
have a cup of tea and a nice hot bubble bath.
:) khairete
S.