Manipulative people latch on to empathetic targets and exploit their innate qualities. They find people who are easy-going, gentle and kind - who avoid conflict and seek to make others happy. The Problem: They reciprocate none of these things. Instead, they feel entitled to your constant forgiveness and self-blame. If you set boundaries or say no, you will be punished for reacting to their abuse. Toxic people constantly look to blame the victim.
Be careful who you take your advice from. Just because someone else tells you something is impossible doesn't make it so. What do you want to achieve? Find people who are doing it and learn from them. If you can't find anyone I guess you'll have to be the first person to do it.