In many apps, you can automatically replace text and punctuation. For example, you can replace a double-space with a period and a space, teh with the, omw with On my way.
How to use text replacements
Open System Preferences > Keyboard >Text
Click the add button + on the lower left
Type in the text to replace (i.e. a typo, acronym, etc.) in the Replace column
In the With column, type the replacements for the corresponding phrases
To delete a phrase, simply click it and then click the minus - button in the lower left.