Memory Sanitization
We tend to romanticize the past by filtering out the less desirable parts of our memories.
Examples
Many people are deeply proud of their military service and praise the military highly. However, when they were actually in the military, their favorite pastime was complaining about how much they hated being in the military. (I can personally confirm this, having served in the U.S. Navy.)
From The Onion: Area Man Always Nostalgic For Four Years Ago