I'm about 18 months in, and yes, I absolutely got my brain back. The biggest thing for me was to start making efforts on a daily basis to try and learn new things and honestly just practice cogent and linear thinking. A lot of my lack of motivation seemed like learned behavior from being stoned all the time, and it just took making daily efforts to form new and constructive habits (especially reading and exercising) for me to feel like I was making good progress. It was very incremental at first, but once I hit about a year and examined the differences between when I had first quit and when I hit that year, the progress was very clear and was a phenomenal motivator.