Well, I usually only use Thinking to serve Feeling (and I honestly use both to serve Ni), as Jung says, but I'm actually aware of logic even when it contradicts what I want. I just choose to ignore it in that instance.
As for how I decide when to terminate, progress, or begin a friendship, I have a set of rules, such as tolerating certain offenses, and not tolerating others, and how often I'll tolerate them, along with a definition of what I consider rude or improper. These rules are fairly fixed for me. The difference between this and logic is that these rules have nothing to do with efficiency or personal gain. They are based on my individual preferences, the things I find distasteful, etc. Also, in some rare cases, I'll make exceptions for certain individuals, but not others. It's arbitrary but organized.