The question of why God allows suffering and injustice is one of the most common questions that a believer in any religion will be asked. It even has a proper philosophical name - "the problem of evil".
The fact that pain and unfairness exist in the world is not a logical problem, nor does it prove that God doesn't exist, nor does it prove that God is evil.
I have no doubt that everyone reading this, without exception, is already well aware that life is tremendously unfair. Our opportunities, health, parents, education, calamities that befall us - none of it is fair. Some people are born into wretched conditions, with birth defects, and have a bad quality of life from cradle to grave.
This is not a startling revelation to the God that made everything, as He knows about this situation and allows it to exist.
A Christian is to keep two things squarely in mind when pondering this:
In light of the first fact, a mere "blip" of 70-80 years of misery pales in the light of a glorious eternity with Jesus in the new creation, where they will never experience pain or sorrow ever again. By the time you've spent 100,000 years in a glorified body, it will seem like a small thing to have suffered for a few decades.
The second fact means that God is reasonable, and will reward those who did even a little, if they had little opportunity, just as He will reward those who did a lot with a lot of opportunity. He is not unjust.
Atheists who dismiss God with the "problem of evil" often correctly point out how absurdly painful existence can be here on earth. There are some situations that can render a person in abject agony for many years, or even all of their lives.
Here we have two scenarios:
For the first case - which applies to every single person on this planet at one time or another - see the above section on inequality. God will right every wrong, and He will judge you taking into account your circumstances that were out of your control.
The second case is a necessary part of having free will. When people disobey God, of course they are going to cause themselves pain, because the Creator's laws mandate everything that is the best case scenario - the perfect standard of righteousness (1 John 5:17). Sin is breaking the Law (1 John 3:4) that was given to mankind to tell them to how live a good, pleasant life that's pleasing to the good God that made them. That's why breaking it causes pain.
In summary, yes, life is tremendously unfair, and for many, tremendously painful. God is not aloof to these facts, and will be completely just and reasonable with His creation when judging them.