When considering a case a tribunal will inevitably take some account of the way people act during the litigation. This is one reason why it’s best to behave in a sensible and reasonable manner.
It is particularly important not act in a way that directly undermines your case. If, for example, the respondent says that you were dismissed for acting in an aggressive and angry manner, try not to blow up during cross-examination. And, if you were dismissed for persistent lateness (which you deny), it is vital that you not turn up half an hour after the hearing was supposed to start.