I had this experience a couple of years ago leaving a previous job. I didn't handle it well. I channelled all frustrations into not eating and went underweight. I thought about the situations too much and the more I thought about them and spoke about them or wrote them down to 'get it out', the more they multiplied in my head.
How did I get past it?
Time, yes, but also some good choices despite how I was feeling. Sometimes it's good to know when your instincts aren't right, and let your head rule the way.
I went for an awesome job I thought was a bit out of my reach. This was my third interview since leaving previous place. My previous job bad mouthed me to one prospective employer (before I showed up to the second interview. My confidence was in tatters after). I'm in a city that's small enough for networks to form. I thought I was ruined.
I went for the interview at the place I am now and as soon as I walked through the doors I felt safe. The interviewer (now my boss) created a great space to chat about my experience. I felt confident and showcased myself at my best. I work with a group of people who are much more mature and professional (most of the time!) I began to trust colleagues again, and trust myself and my judgment. My previous environment was young/cliquey marketing agency and there was a lot of bullying. I've learnt that I'm massively impacted by the environment I work in, and I try to surround myself with people with good values.
Changing environment and the people I worked with helped a lot with moving forward. I got into weights workouts and met new friends through that. Once I started to build my own networks I started to feel more confident again.
I think it took me about two years to see the situation clearly. Not that I'd been thinking about it for two years but by cracking on with things and making some good choices, I was able to reflect on it later and with a more objective mindset.
So my advice OP is what small things can you do? Grit your teeth and do them. Future you will thank you.
I hope any of that helped. Just know you're not alone. You know who you are and no-one can take that away from you. I can't remember who said it but no-one can make you feel inferior without your consent. You have much more power than you think you do. After all, why do you think they were threatened by you in the first place? By lying about you, ultimately they've harmed themselves more.