Phrases

I have some ancient phrases that sound familiar today. Can you help me find the present day phrase.
1 The loss that is unknown is no loss at all
2 While we stop to think, we often miss our opportunity
3 For a good cause, wrongdoing is virtuous.
4 When fortune is on our side, popular favor bears her company

Well, here's some potential more modern alternatives that mean roughly the same things:

1. What you've never had, you've never missed - out of sight, out of mind.
2. Strike while the iron's hot - carpe diem.
3. The end justifies the means.
4. Everybody loves a winner.

There's sure to be other possibilities too.

See also: the meaning and origin of Carpe Diem.