The line "Don't walk lightly into that beautiful night" is now known to many people, because anyone who has seen Interstellar knows that the old professor inside kept repeating this sentence before his death.
The new viewpoint of this poem is actually to express that people should not just be content with the status quo, and should not always be gentle and stable in the present state. There will be many challenges in the future. We should be prepared for danger in times of peace, and try to deal with different situations every day, instead of being comfortably immersed in the present life.
The explanation in Interstellar's films is that we should challenge different fields and places for mankind and seek that bright future for mankind. This poem was written by Dylan Marles Thomas, an English poet in the mid-20th century.