In a sentence that consists of two independent clauses, those clauses should be separated by a semicolon, not a comma. Separating them with a comma but no conjunction is a very common writing error called a ‘comma splice’.
Where you have two independent clauses, they should be (1) separated by a semicolon, OR (2) joined by a conjunction OR (3) broken into two sentences.
Here's an example: ‘It was a long trip home, I had to catch two buses and a train.’
I could rewrite this as:
‘It was a long trip home. I had to catch two buses and a train.’ (separate sentences) OR
‘It was a long trip home; I had to catch two buses and a train.’ (substitute semicolon) OR
‘It was a long trip home, because I had to catch two buses and a train.’ (add a conjunction).
About this blog
Through my experience as an editor, a reader and a book reviewer, I’ve noticed that some writing faults keep just popping up again and again. As an author, I’m especially aware of those writing crimes that I’m frequently tempted to commit myself. This series of brief tips addresses the common writing problems that I’ve encountered. Following them will help make your writing clear, accurate and stylish.