As much as celebrating little achievements are important, teaching kids the important lesson of learning from their mistakes is also important--Managing failure is important. Many people grow without knowing how to handle setbacks which are usually a lot in life. People grow and feel entitled to success and when they are no longer getting their little carrots they become resentful or depressed.
From our failures we can learn valuable lessons that can help us make a better decision by avoiding certain mistakes we might have made in the past.
So, in a nutshell, we need to find a balance between both.