The best feeling comes when :

"The best feeling comes when you realize that you're perfectly happy without the people you thought you needed most."

'I think and think for months, for years :

"I think and think for months, for years.  Ninety-nine times the conclusion is false.  The hundredth time I am right."

- Albert Einstein

When you become really close to someone :

"When you become really close to someone, you can hear their voice in your head when you read their texts."