How should a friend with negative energy explain?

You should accompany and take care of him more and let him know that life can't be smooth sailing and everyone has troubles. It is useless to be negative, it will only bring worse results. Only by facing it positively can there be a solution. Suffering in life is not necessarily a bad thing, but sometimes it is also an experience. If you come out, it may bloom in spring, and it will only get worse and worse if you remain negative.