Since Channel permissions act as individual overrides to Server-wide permissions, they can result in a user accidentally locking themselves out. This can happen in one of two scenarios. Both of these instances cannot happen if you are the server owner. Server owners can access any channel's permissions at all times!
Mallow has been given his own role in Mario's server, labeled "Admin". This role's been given the "manage roles" permission:
Mallow doesn't want Valentina to change the Nimbus Land channel according to her diabolical plans, so he opens the channel permissions settings to take away her role's permissions..
..But he forgot a key step!
You used to be able to lock yourself out of editing channel permissions by denying yourself the "manage channel" or "manage permissions" permission, but no longer! If you try to perform an action that would normally lock you out, the above message will show, and prevent you from slipping up.
To solve this issue, you have to allow yourself or another role the permission before disabling it. Mallow's problem was trying to deny permissions to @everyone before making an exception for himself. To fix this, he went through these steps:
1. Allowing the "admin" role to manage permissions (since Mallow's an admin, this permission will only apply to him):
2. And THEN denying the permission to the @everyone role:
And now the proper permissions are in place! Quick recap:
Keep in mind, this can apply to specific roles, as well. If you disable a specific role's permissions, you can add an exception to your username specifically, and you'll be able to allow yourself that way as well.