As many of you were confused what happened to Sid and asked about Repression, so I am explaining it again.

Repression is basically a defense mechanism. Sometimes a traumatic incident, memories or incomplete desires/wishes give lot of emotional pain. So sometimes person tends to forget them. They are present in out mind but we don't remember them consciously. They can come through dreams and flashbacks at times. They can also be taken out through hypnotism, etc.

It doesn't happen with each and every person. Sometimes it's considered good that the person no longer consciously remember those painful memories but if this happens more frequently, it's a problem. If person starts forgetting all thoughts that cause pain, then it's not normal.

An external brain injury is not required. It happens within the brain.

So Sid never had an accident or some brain injury. Those childhood memories were so painful that his mind repressed them.

It's actually a psychological concept.

Still any doubt?