Is this a cold decision?

[EvolvingPhoenix]

To cut off people completely from your life if they are seen to be ''toxic'' or whatever? be it a family member or a friend you've been with for a decade

A few of them may not be happy with the departure at all.
I knew I will have second thoughts about this. because I'm a fool sometimes.

Have you ever done this? what are your thoughts?

I've been on the receiving end of this and having been on the receiving end, I would NEVER put somebody else through it. There have got to be ways to enforce boundaries without cutting someone out of your life completely.