Moral absolutism is an ethical view that all actions are intrinsically right or wrong. For example stealing is always wrong. Its opposite is moral relativism (the idea that there is no universal or absolute set of moral principles).
Consider the following scenario: John stole something from the shop. Most people would agree that that's wrong. But consider the alternative scenario John stole bread to fead his family. Now most of us would agree that in this second scenario even though John stole something it doesn't seem to be wrong. That would be the position of most people since they consider morality to be relative. I however disagree.
Let's examine those 2 scenarios a little more closely. In the 1st scenario John stole for selfish reasons, because he wanted to. In the 2nd case he stoled because of a greater good, feeding his family. Both of these scenarios have "the act itself" - stealing. So in both cases John stole something, which is wrong, but in the 2nd one there's something more that kinda complicates things for most people, I call it "moral justification".
Moral justification is, simply put, a process whereby a person who is evaluating a morally questionable act attempts to make it seem right. This person looks for a way to shine a favorable light on such an act in order to maintain a clear conscience. Or to put it even more simply it's something that tries to make a wrong to look good or at least a little bit less wrong.
I'm pointing this out because people use it to "prove" that morality is relative. Which is wrong. The "act itself" is what is either right or wrong. So murder is either right or wrong, murder is taking someone else's life, therefore murder is wrong. The murder is murder no matter what. It doesn't matter if it's cold-blooded or accidental, it's still murder and therefore wrong. When it does make a difference is with "moral justification" or why someone did what they did. If it was cold-blooded then the person should be receive much much more harsher penalty than the one who did it accidentally. But as I said it's still murder and therefore still wrong, the difference is in the reason motivation.
To prove to you that what I'm saying is true I'll name 2 examples: raping someone and torture and murder of babies and children. There's no sane person on this planet who would argue that either of those 2 examples are either good or justified. If relativism were true than someone could find a reason to say otherwise but it's impossible because those acts are acts of evil of pure evil. Therefore when we judge if action is right or wrong we only ought to care about the act itself and nothing else. The moral justification should be considered when deciding on the punishment (if there should be any) and similar things, but never with the morality or immorality of a certain action.
How to live moral life?
Knowing that morality is absolute how should we act. Well, we should act accordingly with it. Meaning don't lie, steal, murder, etc. When doing good don't do it because you can benefit from it, e.g. don't return a lost wallet because you hope to receive a reward. Do it because it's the right thing to do. The reward might come, it might not but your conscience will be clear knowing you did the right thing.
People don't realize that everything you do you don't only do to others but to yourself as well. If you do evil, you "stain" your soul with sin. And you gain nothing. Even if you do it's short-lived and will eventually fade, but you with your "stained" soul will have to face God at the Judgment day to answer for everything you did. That's a long-term goal you should be focusing on. You won't live forever on this Earth and when you die as I said you'll have to answer to God. Of course none of us is perfect and all of us are sinners that's what forgiveness is for.
Another aspect to take into consideration is that trying to do wrong things is like trying to twist reality, you can do it for a short time sure, but eventually the consequences will catch you and the reality will snap back at you and it will be really painful. Everything you do has consequences, so be careful what you do.
Very good