I'm not sure how to phrase this, but I think I can be overly sensitive and take things too personally.
One example was I forwarded an email to someone I work with. I didn't know their account was shared, and my boss's boss messaged me saying he saw that I just forwarded it, and that it was not courteous and unhelpful that I did not add any context or explanation of my own (I literally just hit forward because the attachments were sort of the important part). I told him that I had reached out over our instant messenger to let the receiver know the context.
I do not dispute his point. He is right it's better to give some summary or context instead of just forwarding someone an email, especially if it's part of a thread. But his criticism sort of annoyed me and distracted me for around 10 minutes. It may have been helpful if he responded letting me know if messaging them through another channel as a follow up was acceptable so I wasn't left wondering if he considers that an acceptable excuse.
How might I learn to not to take things personally and grow a thicker skin?
Additionally, I can be really bad at knowing when to "defend myself". I know usually being defensive is considered a bad thing, but sometimes it's good to clear up a misunderstanding. In this example, should I have told my boss's boss that I had messaged them through chat or just have said "OK"?
How might I learn to not to take things personally and grow a thicker skin?
That's a question for interpersonal.stackexchange.com not Workplace.