Answer:
This will mean that it isn't a thing to be proud of.
Step-by-step explanation:
My answer will define that dying is sleeping forever, and it's not a mind-blowing idea just to make yourself die. The reason the tone "Death be not proud" exists, is because we want to live eternally. We do not want to shorten (or try to get rid) of our lives. But, to be a little bit concise, this 'underrated' tone is important because here; let's look at the last sentence of the poem.
So, "And death shall be no more" means that we should or WILL live longer. For example, your parents that did so much for you. Maybe your grandparents. I'll suggest living longer is 100% a better idea, so you could bear your mind, or your brain with it to think about it maybe more than once.
*If you do not understand my evidence, I'll be specific. But you can mark me if this helped.* :)