No, you didn't do anything wrong. The Earned Income Credit is calculated automatically by the program and if you are owed the credit, it will be placed on your return. While the credit is often associated with having children, it is possible to receive the credit solely based of your earned income - you do not need a qualifying child (though the amount of the credit will be greater). The EIC would be on line 66a of Form 1040 (line 42a of Form 1040A).
If you have this credit on your return (or the Additional Child Tax Credit), then the return will be delayed this year because of the PATH Act. However, if you are asking this question solely because you got a message from Where's My Refund about topic 152. Please be aware that, while the IRS added language about the PATH Act, that message is actually a generic delay message and your return could be delayed for any number of other reasons.
