Have you ever had a coach where, in hindsight, there were some red flags for training with them? Bad coaching can really have a negative impact on a rider's confidence.
One of the hardest things to do is to walk away from a trainer where there are red flags because the trainer can exert a lot of control over how the rider feels about their decisions. Keep your mental health and your horse's interest in your heart!
This isn't to say that some lessons might be more challenging than others, but there is a difference between a challenge and something more negative.