It means that the past is gone forever, and many things can't go back once they are missed, so you should learn to cherish them now, and you won't be wronged by yourself in the future, and you won't let yourself down and treat anyone or anything.

It can also be understood as: what happened in the past has happened and cannot be changed, so don't indulge in the past, look ahead, and the road ahead is so long that you must not be confused and take it seriously. This belongs to the value orientation of never giving up, belonging to loneliness and stubbornness, never turning back in love, and never lowering the standard of mate selection because of empty windows.

Extended information

The enlightenment of this sentence:

Everyone has only one life, long or short, and everyone goes on, sad or happy; In life, everyone is on a journey, either rising or falling. Days are the blandness of daily necessities; Busy, that is, going out early and returning late; Mood, is the joys and sorrows, incomplete, is the regret of rain or shine. Life, to face yourself, to face the natural world. Open-minded life, broad-minded, forgive mistakes, live calmly, cultivate magnanimity, save a lifetime of happiness, bend over to do things, and settle down to be a man!

Circumstances are born from the mind, and mentality determines the attitude towards life. Positive optimism can make people sublimate their souls. From Su Shi, it is also a kind of wisdom for us to taste tranquility. "If there is no happiness in my heart, even if I travel all over the world, I will never find a paradise; If you are satisfied and happy in your heart, you can be at ease even if you are in prison.