If you feel like all of your work has been for nothing and that you're back where you started, remember that progress works in a spiral, especially with mental health. You may circle back around, but you're a tier up because you know more from your experience. You may have a better grip on what makes you feel better. You are more prepared.
When young people especially have suicidal ideas, those thoughts get integrated into their minds. For many, suicide may even become this back-up plan that is always there as a fail-safe. That's what happens when you have recurring thoughts while your neural pathways are literally reforming (which happens in your teen years). These thoughts are ingrained into your head, and their influence is the effect of something from the past. You are still growing. You are still making progress and getting better, stronger. Just keep your head up. It really does get better.