Here are two reasons why I despise toxic positivity: 


1. It can sound disturbingly similar to the same messages people receive from abusers: “Your feelings don’t matter.” “You’re not allowed to feel anything that inconveniences me.” “Only my problems matter; you don’t have any problems.”  It’s emotionally invalidating and can be very triggering.

2. Toxic Positivity sends the message that your problems are simply due to a lack of willpower (essentially: “your fault”). Just push harder to think differently, and you can. That quickly induces a deep sense of shame in people struggling with issues that require more interventions because of factors beyond their control. It makes it sound like if you need any other interventions (such as medication, relational support, therapy, relaxation techniques, rest, etc.) you’re somehow weaker than other people. 
It also keeps people from offering care to others, from asking for help when they need it, and it promotes a standard of emotion regulation that is neither natural nor achievable. If we only allow ourselves to feel happy all the time, we miss out on crucial information our bodies and emotions are trying to give us, such as what we value in life or when it’s time to set boundaries.