Some of the best tennis players have been coached by their parents. It's not for everyone. However, if you are going to coach your son/daughter beware of the phrase "Just go for your shots. Just go for it. Don't hold back." Only two things can happen from such vague advice, a very favorable outcome where its lights out tennis or a very quick 6-1, 6-1 loss. For any great player, this is far too much risk to assume to achieve a victory.
The moment you say, "Just go for it," you have given the player an easy way out if things don't go perfectly. No matter how well intentioned the advice may be, the player will not interpret it the same way you do. This is why it is very dangerous for parents who have never competed to give such poor advice. The advice shifts the responsibility from the player to the parent.
After another quick loss, the players snaps to his/her parent, "You told me to go for it!!!" Without the parent understanding what they have done, they have given the player an easy way out. Instead of having to face the music, the player can now shift all the blame to their parents (or coach for that matter).
The goal of every match is not to beat Serena or Roger, but to find a way to win on that specific day. Practice matches are the time to "Just go for it" and push outside your comfort zones. When it comes to tournament play, you play the percentages. You fight, scratch, claw, adjust, adapt, survive, compete and maybe if you are lucky, some of the "Just go for it" shows up at the right times.
The best remedy is to not give such advice unless you want to give them a license to tank.