The Canada Revenue Agency (CRA) asks that you choose a code from the generalized list of codes and to choose your code, establish what the main activity of your business is, and find the code that comes closest to it.
The NAICS system is structure under classes of industry. You will decide what class of code you fall under by clicking on the 2-digit code, which generalizes the initial industry, then this will open a new class within the initial one entered, you then continue to click on each entry until you end up with a complete 6-digit code.
If there still is no specific code for exactly the kind of work you do; simply choose the code that matches best. In every classification, there will always be an “other” category, which may be your best option if none fall under what it is specifically that you do.
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Hello @kylie__wyote
In addition to @TurboTaxGinette's answer, ... I also recommend you visit this CRA's web page to filter codes using keywords relevant to your profession:
https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/sole-proprietorships-partnerships/report-business-income-expenses/industry-codes.html
Hint: When I typed "psych", the web site returned 621330 and 621110. Since only you know precisely the nature of the services you offer, I'll let you decide on the most appropriate code.
Have a nice day!