Something that always bugs me a little in discussions about mental health is the concept of 'setbacks'. Frankly, I don't believe they exist. Now, I'm not suggesting that there is a right or wrong way to discuss your own mental health; you should always describe your experience in a way that works for you. For me, the concept of a 'backwards step' or 'setback' makes me uncomfortable, so I'd like to offer an alternative perspective.
There will be down moments, relapses, and times you feel hopeless. You might engage in an addiction, deal with a challenge in an unhealthy way, have suicidal thoughts, or just a gloomy day. 'Downs' come in varying forms and levels, but even if you feel like you've hit rock bottom again, you are not taking a step back. There is no 'returning to square one' in recovery. No matter what happens or how deep into a spiral of bad mental health you end up, your progress can never, ever be undone.
You can't undo the past. This means that regardless of how bad a place you may find yourself in, your achievements will never be erased. The steps you've made in therapy can't dissapear. The times you've faced a challenge and smashed it happened, and can't be erased. The new skills you've learned and coping strategies you've developed still exist within you, even if you're struggling to use them. The new parts of yourself you've found can't be undiscovered. That is why there are no steps back.
Recovery is a journey. It's a difficult one. Some days it'll be easy, and it'll feel as breezy as strolling along a beach or a meadow. Some days it'll be so hard, and might feel impossible, like you're clinging to a vertical cliff face by the fingertips. You can make that difficult climb, because your journey so far has prepared you. You can do this. You know you can get through the tough bits, because you've got through every part of your journey previously, and grown from it. You'll always be moving forwards, no matter how rocky the path. There are no backwards steps on your journey.