If you're going to be a writer, be the best writer you can be. It means using the words you choose correctly. It's probably the English teacher in me, or maybe it's the editor in me. I'm not sure which, but incorrect use of words makes me crazy. It makes me crazier when people win book awards and they have used incorrect words.
I have a list of words you shouldn't use. They are as follows:
Getting rid of these words when you write makes your writing crisper and more to the point. It prevents you from using passive voice and puts you in active voice. I understand these are verbs and helping verbs. They help fog up your writing and put you in passive voice. Both things will make your writing second rate.
My writing is not perfect. I work all the time to improve it. One of the things I've noticed in leaving these words out, my story moves faster. There is action. It doesn't get bogged down. It's moving out of the second rate stage and becoming first rate writing.
The other thing you need to do is get a good editor. Find a retired English teacher who is willing to work with you to make your writing better. Use the Find button on your word program and look for the words on the list. What can you replace it with? Or can you eliminate it altogether? Make those changes.
Then and than are often used interchangeably. They have two different meanings and using them this way is wrong. Then is a time. What happened next? Then we went to the store. Than is a comparison. Sally is older than Bob. Two different uses.
The word 'that' is highly overrated. Don't use it. Most of the time when it is used, it is used incorrectly. It's a space taker and adds nothing to your writing.
Ultimately, you have to decide what you are writing. Just make it the best you can.