I accidentally started two courses but didn’t have enough time

If you have paid for both courses at the same time, as Gent cautious you, then I suggest to cancel one of the course payment or contact the Coursera staff as describe here. Tell them that you will purchase the second course later.
On the other hand, if you have financial aid for both courses, try to complete them in six months as your financial aid will expire after that period. Though you can apply for financial aid again.