This is solid advice if you know for certain that the person doesn't want you in their life any longer.

Problem is, sometimes it's rather difficult to determine whether or not that's legitimately the case; maybe they are depressed or have other mental health issues going on, maybe they've got a jealous partner, maybe they just got really busy with other stuff, etc. I've got friends where we might not communicate for a year or more at a time, and there have been other times where I legitimately thought someone wanted me out of their life only to find out later that was certainly not the case and was due to circumstances beyond their control.

All I'm saying is just be cautious when using this approach. People have deleted me out of their life because they assumed that I was not interested in being friends, just because I hadn't reached out to them specifically in X number of days.

However, if someone clearly communicates to you that they no longer want you in their life, by all means respect their choice and cut ties. It can be difficult and upsetting especially if you care about the person, but unfortunately it can happen and it's best to respect their wishes.