Where a sentence has two parts that could stand alone as sentences, with only a comma to separate them, it is a comma splice:
- I went outside, I needed a break.
The two parts here are both complete sentences and should not be joined by a comma. There are three basic ways of avoiding this:
- Write them as two independent sentences: I went outside. I needed a break. (However, using this too often can make the writing rather choppy if there are too many short sentences.)
- Separate them with a semi-colon: I went outside; I needed a break.
- Use a conjunction: I went outside because I needed a break.