I have only one true motto in my life: Don't fret, act. It stems from Buddhism, actually, but is more directed than just saying "stuff happens, and you can't change that".

To every worrying, anxious, sad, fretful person out there. I feel no sadness for you because you have chosen that path.

I'm often reminded of the great Rush (Freewill) lyric: If you choose not to decide, you still have made a choice.

Fretting is choosing not to act and it's an incredibly useless as a tactic.

As Yoda says: Do or do not. There is no try.

Make your luck.