Pressure can build and pressure can damage. Too little pressure and the player is not able to achieve his full potential. Too much pressure and it can lead to trauma. So there is always a fine line we must be careful not to cross.
Have you heard stories of players that have been so traumatised that they quit chess? I have. Chess is very very intense. And most children are not yet equipped to handle those levels of pressure. That is why postmortems are very important if only to ensure that the player is not damaged. It's not only the technical.
If this is done properly, the player will play each subsequent tournament with equal vigour. That is the trick.
So this means the player must be properly prepared mentally, properly trained. He is realistic in his expectations. This means that there must be accurate measures. If not he will return from each tournament a little more damaged and eventually he will lose the will to fight.
Fragile talent can easily be destroyed. We must be watchful.