I remember this stage when I started taking SSRIs when I was an older teenager. I was warned about it and was seeing a short-term therapist and so I dealt with it well, but there's a short 2-4 weeks where the crushing demotivation that has dominated your life is lifted but you still are stuck in the life-despising thought spirals. I assume that much of this can be mitigated by regular consultation with mental health for the first two month while trying a new medication, but it's possible that isn't true.