Uncomfortably Comfortable
An example of this could be:
1. A low paying client.
You don't want to lose the low paying client in case you don't find a better paying client. You worry about not being good enough and your protective brain then rationalises this fear with 'it's better to have some income than no income' ... but in reality the low paying client is just holding you back from spending the time finding better clients who will pay more. This will then give you the ability to start building your team because you have the money to do so.
2. A relationship.
You don't want to lose the person you're with in case you don't find someone else better. You worry about not being good enough and your protective brain then rationalises this fear with 'it's better to have someone rather than no-one' ... but in reality the 'not-so-great' relationship that you're tolerating just feeds your low self esteem even more, making you ever more unhappy over time. Holding you back from treating yourself right, and spending the time to find someone better for you.
The moment you don't think you're good enough, you settle.