Is the glass half full or half empty?
If you fill the glass up halfway, then it’s half full. If you consume or waste half of a full cup, it’s half empty. This could be taken as “Life is what you make it,” since your behavior concerning the glass determines whether it has been filled or emptied. But I mean it to mean that most people tend to evaluate the glass based on whether they have lost or gained something in whatever real life situation they are comparing.
If your glass is half empty, there’s good news. Just dump the water out and put it in again and voila, your glass is half full. And unless you’re ungrateful from the get go, you can’t ever make a half full glass be half empty.