You folks are correct in trying to understand what is in your (and/or your son's) control. Many coaches try to get players to understand the same thing. Another thing coaches try to convey to players is to avoid getting too high or too low......good advice for parents, too.
We have to remember that as important as baseball is to our boys, ultimately there will be many more things in life that are more important, that will break their hearts much more and create major distractions in their lives as well as allow them to experience the great joys that life has to offer.
The guidance of us parents and the example we set for them, the strength that we exhibit, the love that we provide for them and the support that we can offer to them as individuals as well as members of a team.....those are the things you have all been doing for the first 18+ years of their lives......there is no reason to change that, even though things aren't always going as smoothly as they usually do.
For most (if not all) of the parents on this site, your children have been raised with a fabulous value system......now they are becoming independent and can put that value system to work.
People can control their emotions by controlling their thoughts, since our thoughts (which we choose) influence our emotions. This is important for players and parents. We choose our thoughts, and because of that we create our emotions.....whether they are positive or negative.
No matter the path, it is only a roller coaster if we make it one.......I know that in my own personal life (yeah, the one outside of baseball) I have also had to learn that I cannot control what any other person says or does, but I can control my thoughts and thus my emotional responses.....same way in baseball.