The saying “This too shall pass” can be interpreted in multiple ways. It can be comforting when times are bad, or a reminder to appreciate when times are good. It is also a reminder that attachment causes suffering.
When things are bad, I always forget that things change. I often feel like “this is my life now. Forever”. Remembering this saying helps make the unpleasant more tolerable.
On another level, this saying is a reminder not to cling too closely to anything external as a source of happiness. We all age. Friendships change. Basing our happiness on changeable things give us a very unstable foundation.
Another interpretation of this saying is that it is a reminder to appreciate the good in the present, as it is. Let’s be grateful for what we have now.