It is important to understand this because it has to do with a major purpose in God's redemptive plan. When we consider mankind and the fall from God's perspective we have disappointment and heartbreak. The crowning glory of His creation, made with the social capacity to love Him and love each other instead hates God and hates each other. In the second generation from the fall we have the first murder, and humanity only gets worse from there. Thousands of years of history, most of it composed of man doing unspeakable things to his fellowman. This is our history as humanity.
That is not the end though. God has purposed through Christ to restore and actually improve everything that was lost in the fall. God has purposed that Christ is to be the firstborn among many brethren who are conformed to His image (v.29). This is greater than a mere restoration of man to Adam's state before the fall because Adam was morally neutral, whereas the nature of Christ has a positive bent towards doing the will of God. Since mankind will no longer have the fallen nature of Adam the curse which restrained that fallen nature will also no longer be necessary.
The curse was never an unmitigated evil, it is a good thing given the current condition of man. Death is the last enemy which God will defeat, yet death serves a purpose in this current world. Mankind becomes very accomplished at what it practices, and when you consider how wicked man can become in the relatively short lifetime he has now, it would be truly frightful to imagine how much worse he would be given a longer lifespan, especially an eternal one if his character was unchanged. That would hardly be a good thing. Likewise sickness is useful in this present condition since all pain tends to soften humanity and remind us of our mortality. The aging process is another thing which is often disliked by people, but which serves a useful function in this current order. When we are young we are more energetic and one of the byproducts of that is that we can misuse much of our time. As we age we are forced to decide what is really important to us and focus on that as we no longer have as much energy as we did when we were younger. This is a blessing, if we lived our full term and yet never felt any aging and then suddenly departed when it was time, we would have much less impetus to focus on things that really matter.
Nevertheless even though these things serve a purpose now, they are enemies. They will not be with us forever. When mankind has lost the nature of sin, and is fully redeemed with the redemption of the body (Rom. 8:23), then there will be no need for these burdens, since man will desire to do the will of God without the sin nature that used to fight against himself. Christ will then have completed His work of redemption having brought man back from the fall and forward to something far better than was ever lost and beyond what we can really conceive. Then He shall see the labour of His soul and be satisfied. Even so come Lord Jesus. Amen.