How can I fix Cydia error: Wow, you exceeded the number of package names this APT is capable of?

Sometimes Cydia on jailbroken iOS devices will run out of space in its data structure to host packages. The default repositories already contain approximately 40,000 packages, which leaves space for an extra 25,000 or so from repository sources added by the user. If this number is exceeded, you might see several errors including:

Wow, you exceeded the number of package names this APT is capable of.
Problem with MergeList
The package lists or status files could not be parsed or opened.

To fix this problem, follow these steps:

1. Open Cydia
2. Navigate to Manage -> Sources -> Edit
3. Remove some of the extra repositories listed.

To prevent this error, you can remove new sources after you download the packages you need. Normally, you would keep the default sources including BigBoss, Dev Team, ModMyi.com, and ZodTTD & MacCiti as they are the most frequently used.