Well it's one of the most important aspects of our lifes so yeah I think it's a good thing. You have to see it from a perspective though - I don't know how you see things right now...

Do I believe in sin? I think that's not a real question in the end - hmmm how should I express this? Well a sin is something that in the end doesn't really exist. It only comes into existance by comparing things to a premade list consisting of good and bad things making it sort of a subjective thing. I don't think that there is a being the Christianity calls God that judges our doings if you mean that bringing up some sort of single definition of what's a sin and what not...

Our lifes are about what you came up with: This total cut-off from e.g. the knowledge about former lifes and also many more things. At the same time you have the possibility to do whatever you want without any restriction. Life now is about exhausting this freedom and learning while doing so. So even if you are the meanest, most evil person on the entire world and you do horrible things that's doesn't make you "bad" or makes your life less "worth". You weren't given all this freedom without meaning. Maybe this sounds like a confusing concept at first and is a "pro anarchy" or "survival of the fittest" argumentation but it really is not. Many religions tell you certain things are bad and threat you with punishments of all kinds when doing those but that's just half the truth and of course tries to bind people to them by using the fear factor...

You were given the ultimate freedom and you won't get punished by actually using it in a way that someone defined as "wrong". There most certainly exists a concept though which is / could be called "Karma" (it imo isn't a much better word than sin though as there are many definitions of what "Karma" actually means). This once again isn't about punishment but rather a concept of actio=reactio. To simplify it a bit and give an example: If you're an oppressor in one of your lifes you most likely might find yourself in the role of someone oppressed in one of your next lifes. So there is a consequence in your doings but it's no punishment and also no judgement in terms of good and bad - just a consequence...

Yet again this also might sound a bit confusing as there seems to be little sense in e.g. playing Ping-Pong between two roles. In the beginning I said something about learning which life is about. When you think about it a bit more you might understand the direction which sort of is given and you can only really reach, understand or even better "live" by actually having learned in your lifes...

There's a lot more about it but I hope I have given you some kind of start or overview...