Loosing your calm, and specially losing your temper, is terrible idea.
Not only you will have personal issues of feeling terrible, you can actually ruin your reputation before you even start working in the field.
If you apply locally\in small scale country, this can result in total inability to find work because you will spread your bad reputation among potential employers.
Main thing about it is not “to remain calm”, but to “respect others” and not lose it in presence of others\empoyers, and sending any communications in rage is extremely terrible idea as well, because that can actually be documented and stored, meaning that you gonna get marked as “non comparable” for them instantly.
You need to behave like professional if you want to become one, and only lose it when it will not affect comfort of other people. Otherwise you practically force your temper on unrelated people, and no one will want to work with person like that.
If you have issues like that, first thing you need to do is to learn how to calm down and not lose it, do not try to apply for a job until you are confident you can manage yourself, because undoing spread of bad reputation can be really hard later.
As for how you can stay calm, I would say main thing would be confidence. You need to build up your confidence, BUT, very big BUT that lot of people miss, you need self-aware confidence, where you are confident in yourself because you are honest about what you can or can not do. I think major problem that leads to issues like that is confidence that is built on dishonesty with yourself about your own ability, which results in situations where potential employer can see you as dishonest person who can not confirm skill set they listed on the portfolio.
You may think that this is rare or untrue, but I saw recent surveys locally and some articles, and to put it into perspective, from perspective of employers this is results they shared:
- When asked to resend resume and portfolio, only 3 out of 10 candidates actually managed to do something as simple as that!
- When given simple step-by-step guide on how to format your application in email, more then half of the people could not even manage to follow simple instructions like that or just can’t read properly
- When people wrote “good knowledge of language X, can do interview in it” (spoken language, not programming), majority of those could not even properly speak in native language, and became completely incoherent in language X
- When people were asked on why they put X or Y on their resume, majority put there not things they have actual experience and deep knowledge of, but things that they got “cerfificates” for, or did some lessons etc, without making sure they actually can practice in non theoretically
And list goes on.
As you can see if you want to get hired you need to be honest and reliable.
Rage is not a problem, reasons of WHY you are mad are. Do you think you were good candidate? Do you think you were not good one? What you are mad on? Can you change X that makes you mad? If you want to solve it you will need to ask and answer those questions.
If you were good candidate, they would hire you. It is simple as that. If you did not get hired, your first step would be to figure out WHY and ask potential employers on feedback, so you can change that. But if you will rage instead of reflecting on failures, you will just keep doing failures.
You failures are here to teach you how to succeed, because by looking on them you can answer question of “what did I do wrong”. So your first step after rejections should be to ask on why you were rejected, not rage on them. Does not matter if you are mad. Blow it off in unrelated area and come back after getting calming down, then write email for feedback or contact them.
If you are getting interviewed on site by an working engineer and not HR, make sure to ask on what they think about your chances and level after you done. Non HR people will generally be more open and might tell you things you will need to hear. But you will need to fix attitude for that, that is for sure.