How do you fix a character you're having trouble relating to?

There are two answers to the question: a short answer and a long one.

The short answer:
Kill them. If the writer can’t relate to them, they won’t portray that character as a three-dimensional being and the reader won’t relate to them either.

1. Take them out. Remove them. Cut their scenes completely.
2. If the scenes are necessary, combine that character with another character if you can, so that one character does the lot.
3. If you can’t do that, replace them with someone who works.

The long answer:
If the character is your main character, you have a greater problem. You need to work out why your character isn’t working, and fix it. I use a gateaux approach to this problem: layers, upon layers.

1. Go back to the character’s Goal, Motivation, Conflict (GMC) statements. If you don’t have any, write them.
2. Make sure the GMCs dovetail into the plot. If your plot doesn’t support your character’s conflict, or strain their motivation, there’s no reason for that character to be in that book.
3. Make sure your plot provides lots of opportunities for your character to show their strengths and weaknesses.
   1. If all they’re doing is stepping through the plot points, with action and response related only to the plot, not the character, the reader (and the writer) aren’t going to have any opportunity to get to know them.
4. Your character has to be more involved in the plot than the reader.
   1. There has to be personal risk for them. Make it happen.
5. Check your writing.
   1. Read through all the action scenes involving your character.
      1. What do their actions tell you about them?
      2. Why do they react the way they do?
   2. If your character is a POV character, find all their introspection.
      1. What do their thoughts tell you about them? Do they waffle? Are their thoughts related to the plot?
      2. Do they go round and round on one particular problem without moving forward at all?
      3. Make them work out how to fix their problems, then stick to it.
      4. If they must revisit the same thing, make sure they’ve moved forward a little bit at least, or that there’s a believable trigger that sends them back to where they started from.
   3. Look for passive verbs, long sections of beautiful prose that don’t advance the plot—anything that slows the action.
      1. Remove them.
      2. Rewrite it so it’s more closely linked to the action.
      3. If the writing is too beautiful for you to change it or delete it, remove it from the story and make it into a promotional post on cut scenes.

Now it’s time for me to take my own advice. The main character in one of my stories has a tendency to cycle through the same old problems without moving forward. It’s got to the stage in the story where I’m rolling my eyes and telling him to build a bridge and get over it—and I created him.