歲月如歌 (The Past Years are like a Song) - Eason Chan

I really like one line of the lyrics

但你手　如明日便要遠離 願你可以　留下共我曾愉快的憶記

Translated that into English, it means

If you are leaving me tomorrow, I hope that you will remember the happy moments I once shared with you

I once heard someone said that human beings are very good at torturing themselves: whenever they're idle and have nothing to do, they'll usually recall the sad memories. Why don't we think of the happy things instead? :P