As responsible parents (and I hope that nowadays there are still a few around) we do have to teach our children to different outcomes of the situations. They can fail, or have success, be disappointed, get rewarded or be refused. Everything counts.
Sometimes we refuse to give them things that would make them harm and when they get a bit older, they understand our choice. It was protection. Other times they don't get a thing that would not cause them direct harm - they will understand it just when they are mature enough, that it was a lesson called preparation for life. Still, they will have to learn how to choose between bitterness and serenity as possible responses to different circumstances. The previously learnt lessons and own responsibility to make the effort for sure can help to make the right choice.