Fixing posture permanently is like finding a lost key in a river and I am the right person who can answer this question since I had gone through this question in my past when I had poor or bad posture. You can fix your posture permanently if you know the right process and you are doing the stretching and strengthening exercises in the correct sequence. In order to fix posture permanently, you must know what kind of posture you have, like you may have a flat back posture or swayback posture. Sometimes it is better to get your posture assessment done by the posture experts. The most important reason to understand the posture type you have is to avoid doing wrong exercises since when I was searching on the internet I too have misunderstood my posture wrongly sometimes. If you want to do self Assessment of your posture you can check out this article Posture assessment and correction
Steps to permanently fix posture
Step 1: Make sure you have identified the strong and weak muscles by doing self-assessment of your Body
Step 2: Once you know the strong and weak muscles start stretching the strong muscles and strengthening the weak muscles.
Step 3: After doing exercises maintain good posture while sitting, standing, and sleeping.
The above steps should help you in fixing your posture permanently. If you want to know more about the advanced process and steps to permanently fix posture quickly like within a month you can contact me on my mail or you can fill the below form and I will contact you. I am a very friendly person and till now I have helped around 15 peoples who have come through my website and asked for posture correction solutions.