If you ever want to feel good again you need to get off this shit permanently. Methadone while a "quick fix" to get off other fast acting opiates does work wonders but like others said it shouldn't be a permanent thing and will make you fat as shit.
It allows you to get through the day without obsessing about getting an opiate fix and lets you live fairly normal. As soon as you get stable you should think about weaning off. It's hell on your heart and gives you a sweet tooth and slows down your metabolism and messes up your digestion and pretty much makes you lazy.
Getting off methadone is a fucking bitch but can certainly be down.
People can get though detoxing but what screws up most is PAWS (post acute withdrawal syndrome). They can be clean for 45 days and still feel like shit. Insomnia, diarrhea, restless leg syndrome, chills, lethargy, headaches and on and on. So they say screw it and go back to using.
When this happens they no longer have a tolerance and usually end up ODing. it's what happened to Philip Seymour Hoffman.
This is what causes PAWS. When you use opiates your brain develops many extra opiate receptors that want to be filled with the influx of opiates. Hence, the user developing tolerance and having to use more and more opiates in order to fill these extra receptors and get the same effect.
When you stop taking opiates 2 major things have to happen. One, the brain has to heal and go through what is called an opiate receptor reduction (closing down all the extra opiate receptors) and at the same time your brain has NO endorphin production due to all the extra opiates that you've put in your body.
Your own endorphin production has to start up and the extra opiate receptors have to be shut down. The longer you've taken opiates, the longer it will take your brain to heal. There's nothing you can do to speed up the receptor reduction that has to take place but there certainly are things that will speed up your endorphin production.
Listening to your favorite music, having sex (a lot), and the main thing, start to workout more and do cardio to amp up your endorphin production.
But it can be done. As long as you use, be it suboxone or methadone it will be a ball and chain wrapped around your neck. That's not a way to live.