I’m sorry about the soul-sucking coworkers and the outright rejection. It sounds painful and frustrating. Anyone in your position would be frustrated; it only makes sense!

We can look at your situation from two points of views, and each point of view will reveal things that can help you better deal with this situation.

The first point of view is the external one, the observable behavior, the one you'd notice if someone followed you and your coworkers/managers around with cameras. Looking at your situation from this point of view, it sounds like there could be a broad problem with your company's management. If so, there might be very little that you can do directly. Depending on whether you want to take upon you a massive, perhaps Sisyphean task (pushing a massive boulder up an infinite mountain, with no end in sight), you could check out the management or Agile literature.

By learning what good management looks like, you could be in a better position to accept rough situations, in the same way that understanding how a cold develops could help us accept feeling drained of energy, coughing constantly, and having to self-isolate to avoid spreading the virus. It's not a solution, but it gives perspective. Beyond acceptance, in the unlikely scenario that your company empowers you, you could propose effective changes or implement them. However, I would not count on this.

If you cannot change your company's management, there are alternatives. Let's go from the external point of view to the internal one, your point of view, the point of view that notices emotions, feelings, memories, action impulses, bodily sensations, interpretations, predictions, etc. From this point of view, we can see your frustration, your fear of being thin-skinned, your interpretation of potential rumination. In this other, internal, world of thoughts and emotions, we can't do the same things that we do in the external world. We can't get rid of thoughts. We can't magically transform them.

Others have recommended simply brushing these experiences off, as if they don't affect you. However, humans hurt where they care. Things that hurt you reveal where your values lie. If you hurt when you see injustice, then justice is a value you hold. If you hurt when you see brutal rejection, then inclusion and kindness are values you hold. It's inevitable to feel pain when you value something. It's human. And it explains why you're hurt; something in you that you value was violated by this experience. A good question to discover what you value is "What would I have to not care about for this not to hurt?" Finding out your values helps you get motivated and gives you purpose, even when the going gets tough.

Still others have talked about changing the way you interpret the situation, including doing it by exposure therapy. This can be effective, as it fundamentally is changing the way that you relate to your thoughts and sensations. However, it's important to do it with the right motivation. Otherwise, the exposure itself can backfire and reinforce the wrong schemas. What is the right motivation? Well, why would you find it valuable to continue in this job, despite its painful experiences? Maybe it brings stability to your life. Maybe it finances other projects of yours that you find valuable. It's up to you to decide. If you do find it valuable, then you will be better equipped to push forward even when the going gets tough. I'm not saying this is the only path; again, it's up to you.

Now, as to pragmatic things that you can do in this internal world, I’d argue that the single easiest, low-risk thing that you can do with the most positive impact is doing the Healthy Minds program or something like it. It will teach you to relate to your thoughts in a healthy way, as well as develop better ways of relating with other people and with your everyday actions, including your work. This will help you regardless of the path that you choose. If you're willing to invest more to reap more rewards, you could consider therapy such as Acceptance or Commitment Therapy or Process-Based Therapy.