Unfortunately, not all firms are well run! Not all managers are calm, fair and objective when it comes to reviewing performance. Never forget, your boss has a boss too, and he/she will be worrying about how to present his/her performance as a manager to the next layer of management. Budgets for bonuses may be limited, so some managers will act tough and try to deny successes. Other bosses will want to build a reputation for themselves as a demanding taskmaster.
So it could be that things get a bit unpleasant. Try to remain calm and factual. Don’t whinge, make feeble excuses or blame other colleagues for where you have failed to meet targets. Be honest and objective about what has happened. Put your hand up if things really haven’t gone too well, but stay positive about how things could go better next year. If more training would help you do your job better, now is a good time to mention it.
But if the conversation is getting out of hand, as it sometimes can in extreme cases, you should call a halt to it. Quietly thank the manager and say that you do not think the meeting is proceeding properly. Get up calmly and leave. Ask for a trade union representative to accompany you to a rescheduled meeting, and let the HR department know what has happened. You deserve a fair hearing, not a blame session, and it is up to management (including HR) to make sure this is what you get.