When we look at our planet objectively, we see that we are insignificant. Therefore, we need to stop acting like we are significant, and instead act like we are significant. If that statement sounds illogical, you are already beginning to understand the folly of seeking meaning in an atheistic worldview.
This can be seen in Carl Sagan's quote in the header image. Using a highly zoomed out image of our planet, he reasons our conceit is foolish (and he's right), and so he concludes that we should be kind to one another and cherish the earth, because we can't live anywhere else.
Flaw number one with his reasoning is that it argues against viewing human beings as particularly significant while simultaneously arguing that we are. All he really does is shift the significance from conceited people to the objects of our kindness. But if a conceited person is not as significant as he esteems himself to be, then by what reasoning do we assume the objects of our kindness are as significant as we esteem them to be? When we are kind, we are making a statement: "You are significant enough for me to do this".
But Sagan and his ilk are arguing this based on a picture so small, not a single human being is discernible. If you zoomed out further still, to the point where you could see the whole of the sun, you wouldn't even know the earth was there if you didn't already, much less that it was populated by people. So using this logic, why would their actions matter at all?
"Because we live on the earth". For a time, yes. Most of us will be lucky to live to our 80th birthdays. A time will come for all of us when we will die, and our earthly bodies will perceive absolutely nothing. We won't remember the past, we won't hope for the future. Good life, bad life, irrelevant. Short life, long life, irrelevant. Poverty, prosperity, irrelevant. Our memories will perish, and the memories of us will perish. Even this little blue speck, left to itself, will eventually be unsuitable for life, and to add insult to injury, that sun on which we rely so heavily will explode, taking us with it.
Furthermore, this logic cannot be applied consistently. Do Sagan, and those who think like him, apply the logic to, for example, the animals he ate on a regular basis? While some atheists are, Sagan was by no means a vegan. He was comfortable with, and actively participated in, the way in which our species consume others. We have enough trouble convincing our own species to see each other as equal, but to remain consistent, Sagan would have to argue that pigs, cows, chickens, sheep etc. are also owed a higher degree of respect.
Sagan had the right idea, but like burying your valuables in the sand when you go swimming, it is based on a shaky foundation. Once buried, you may forget where you left them, or the tide may come in and ruin them, or a thief may dig them up and take them. Kindness is a virtue for which we should all strive, but atheism is a worldview that makes it utterly futile.
So where do we go? To the God who made us, sustains us, and loves us, of course. To Him, we are both significant and insignificant at the same time. He has access to all perspectives at all times. He holds the past, present, and future, all at once. He sees the furthest corners of the universe, and the tiniest crevices in our world, at the same time. Beyond all imagination, the God who knows every star by name, and has to humble Himself to see our world, humbled Himself even further to become one of us. God lived on this little speck! And He suffered the scorn of conceited men. Men so foolish, they believed offending them was a crime worthy of death. So what did they do? They killed Him. All the while, as He taught His disciples to do, He prayed for them, His enemies: "Father, forgive them, they know not what they do".
In His death, He bought that forgiveness for them. The greatest form of kindness is that offered to those who are worthy of wrath, and Jesus both preached and practiced that we should do this. This is why what we do here is significant. It's not because we're insignificant compared to the universe, it's because we're significant to the God who created it. When we are kind, He remembers it. When we are evil, He remembers that. But one must outweigh the other, for they cannot coexist.
The problem we have is that we have all done evil in His sight. We tend to downplay it, not realising how disgusting we are for the same reason we can't smell our own farts. As our eyes can see the nose in front of our face, yet our brains automatically ignore them, so also is our ever-present evil invisible to us. But when we look in the mirror, we do not ignore our noses, and when we look at the law, we know we have violated God's precepts. For that, He must pour out His wrath. But on whom is open for wriggle room.
When Jesus died, He made propitiation for the sins of the whole world. God poured out His wrath upon that cross, dealing with sin once and for all. The Bible tells us that Jesus, who knew no sin, became sin for us, that we may become the righteousness of God in Him. Therefore, all who believe in Him, confessing Him as Lord, and believing He rose from the dead, will be saved.
And so we see the stark contrast between atheism and Christianity. Christianity offers what the atheist wants, but is at this point too conceited to pick it up: Consistency. It is fully consistent to say that all who bear the image of God are significant, and thus we should obey Him by honoring them. But where is the consistency in saying we are so insignificant that we should treat each other as if we were significant? It is fully consistent to say that we are not a mere accident, and our purpose is to obey God by loving Him, and loving one another. But where is the consistency in saying we should love the cosmic equivalent of a milk spillage? Only Christianity can account for the significance we feel we have. Atheism does not prevent the feeling, but limits it to just that: A feeling.