Employment tribunal hearings are stressful, and lots of people become more compliant and suggestible under stress than they are normally. (Many people are scarily compliant to start with, as the Milgram experiment notoriously demonstrated in 1961. )
This can mean you’re so busy conforming to what you think is expected of you that you don’t assert yourself when you need to.
In particular, if you are representing yourself, you may be doing your very best to conduct the case as if you were a professional lawyer. That’s a good idea, up to a point. But if this isn’t something you do all the time, you will need a bit more latitude than a lawyer. A lawyer is expected to have read the legal authorities relevant to the case; to understand any technical terms used; to be ready to make submissions immediately after the evidence is finished; to be able to read and assimilate new documents quickly. None of this necessarily applies if you are representing yourself.
So if the other side gives you some documents you haven’t seen before, ask for time to read them. If the lawyer on the other side or the tribunal uses technical terms you don’t understand, ask for an explanation. If you need to collect your thoughts after the end of the evidence before making your submissions, ask for a short break in which to do so. If the other side gives you some copies of law reports they say are relevant, ask for enough time to read and understand them.