The Problem with Self Inserts
There is nothing wrong with inserting yourself into a story. Like anything, it can be well done or... not so well done. The fact is, the majority of people who tend to write about self inserts happen to be beginners. Naturally, that causes there to be a pattern of certain, specific mistakes that are frequently found whilst reading anything on the internet. The purpose of this deviation isn't to say that self inserts are bad. I'm simply going to point out the most common mistakes that we usually encounter.
1. Making ourselves better than we really are.
Don't be fooled by the word "better." This can be replaced with mysterious, deep, dark, tragic, romantic, lovable... anything we want. Maybe a mix of a few of those things. The point is, the version of ourselves will be biased.
2. Not making anything bad happen to yourself
Let's talk about the word "bad." Does this mean something, perhaps, like... getting a disease? No. It means anything that interferes with the biased image you want to portray (whatever that might be).
3. Getting big headed
Sometimes people who write about themselves start thinking about themselves waaayyy too much. They even begin to believe their own biased images of themselves (or worse. Think that everyone else falls for it too).
4. Falling into the trap
"I know! I purposely won't make myself perfect. I'll keep saying that I hate myself!"
C.S. Lewis said it the best: “True humility is not thinking less of yourself; it is thinking of yourself less.”
It's not about what you (or your character) would say when asked if they think they're special. "I'm the best!" "I'm the same as anyone else," and "I don't deserve to be here," are all irrelevant, meaningless phrases unless you, as the author, prove it in the way that you PORTRAY the character.
Nobody makes a Mary Sue on purpose. They are all unconscious. How many stories have you actually seen with a stereotypical Mary Sue in a pink princess gown who says, "I'm better than everyone!" and is supposed to be? Give me a big, fat break. Let me make this clear:
NOBODY IN THE WORLD WRITES THAT WAY.
That is a fake, stereotype of Mary Sue made up by dumb people to feel good about themselves for not being like nonexistent even dumber people. The same people who thought they were smart for saying the world wouldn't end in 2012 when NOBODY sincerely believed that.
I'd say 100% of Mary Sues are characters that the author believes is a good character.
But I'll leave it at that since I already have a rant about Mary Sues (see link in description).
I'll be honest. Most good characters ARE self-inserts. And this is what I mean by that:
ALL well-written characters we create, inevitably have parts of us inside of them. That is actually HOW characters are well-written: because the author could relate to them and knew what they were talking about.
I know from experience that it's possible to write about characters that are over your head, and that is usually when they are poorly written. When you have a character like this, it's best to try and find a part of them that you can relate to, or at least look to real people so you can do a kind of imitation. Just make them real.
A word of advice: if you don't understand your own character, nobody else is going to. If you can't get into their head, their head will never be worth getting into at all.
I have nothing against self-inserts. I think inserting parts of yourself into characters is actually *necessary* (well, as always, depending on the style of the story. Naturally in a picture book or something it isn't that important. Again, make things deep enough for whatever you're writing). In fact, I think it's your best (probably only) bet at making a good character at all.