My manager is very impatient and often criticises me. I cant take criticism well and have a low threshold of stress. What can I do to get stronger (to cope) on my own and without changing her at all?

You will need to know that whatever happens at work, don't take it personally its just business. Give yourself some space and time if needed to deal with the stress or emotions. Excuse yourself if you must to do so.

Practice taking criticism. Have a role-playing session with your friends for fun or with yourself for privacy, and imagine the worst criticism you have received and could received. Imagine different ways you could repond to those: bad ways and good ways both. Imagine how you have responded in the past, and one thing you could have improved on and how. Consider why you don't take criticism well, and what's underneath that. Is there something you can change there? When your manager says something cruel to you, imagine in your head something funny they could have said instead, or the way they could have said that which would have motivated you instead (you don't have to say it out loud to them, just think it amusingly to yourself.) Reach out to your coworkers and see if you can make friends with one or more of them: they may feel the same way, and their comradery will help you stick around there longer. If your stress at work interferes with your day-to-day wellbeing, it may be in your best interest to jump ship and take the healthy risk of finding a healthier working environment.

This is a difficult and stressful situation, and how I tried to cope with a similar kind of a situation was by telling the person how much I was trying and that the person's criticism was really hurtful. Try not to make any promises that you are unsure of your capabilities of fulfilling and be honest.

just try to ignore him and smile when he is bullying you, stay strong and realise if he is hurting someone that means you're better person than him,

When she speaks, pretend it's your favourite comedian. Believe me, your manager seems like she's got her own issues in the first place.

Just count to ten every time she criticizes you! Distract yourself and if it helps think about the money that you will have when you get your paycheck:) It will make it seem like less of a problem:)

Understanding, understanding, understanding. When I get fed up with my cyclical trap of stress, I just need any different emotion as a stimulant, I don't even discriminate emotions at the tipping point of stress. Work is a particularly challenging place for me to manage my emotions because I understand that these people don't know where I came from to be the person I am. Accept that your manager may not ever know you as well as you do, and accept that you are stressed and struggle with the criticism. Also, no manager is perfect and they make mistakes. Taking deep breaths and learning to protect oneself at work, internally, can help to demonstrate to your manager that, hey, yes what you are saying does bother me, but I am still me and I am trying. Perhaps, asking what suggestions the manager may have, to improve yourself at work, and view what you feel you can rationally handle. Change is gradual. Just because your manager cannot be patient with you, doesn't mean you also need to accept the way they treat you. The best thing I can suggest, is to find another emotion or thought process to substitute for the stress. Something that may help you and your manager, simultaneously, to streamline the criticism.

Learn from the criticism and mistakes. Be acountable for your actions and do not take things personally.

I have struggled with criticism myself, because I thought it meant I wasn't good enough at my job. Then I'd find myself very upset with me, and thought my boss didn't like my work. Come to find out, it was only one aspect of something that s/he would want me to work on improving. When I crawled inside and thought negatively about the criticism, I couldn't see where they wanted my best interests at heart. Maybe ask yourself what makes criticism difficult and what emotion is getting challenged for you. Is it really the criticism that is challenging you? Do you recognize any internal thoughts about you when hearing critical feedback (which can be very good for us to hear - though hard to hear)

Just keep reminding yourself that this has nothing to do with you, or nothing is wrong with you... Do your best with whatever task is assigned to you, and then simply step back, and stay calm. Don't let this affect your self-worth and personal life.