This rule might seem harsh, but at your core you know it to be true. In the beginning, you gave the tenant a second chance, and then after that, a third. A tiny voice in the back of your head told you that it wasn’t going to work out, but you kept shushing that voice because you didn’t want it to be true.
Every month that you leave a non-paying tenant in your property, you increase the likelihood that 1) the tenant will cause damage to your unit, 2) the damage will exceed the security deposit, 3) even if you obtain a judgment against the tenant, you will not be able to collect it, and 4) the tenant may file for bankruptcy and you’re stuck with them for a long, long time.
Landlording is not a business for people who don’t like to be proactive; either stay on top of the business or hire someone who can.