How do I handle the auxiliary verb 'izan' vs 'ukan' in a real conversation?

I have my first conversation with a native speaker from Gipuzkoa next week, and I’m terrified of picking the wrong auxiliary. I know the basic rules, but I'm worried about freezing up when I have to conjugate them in real-time. I’ve been using Chickytutor.com to simulate these dialogues and get instant corrections on my auxiliary choices, but how do I stop being so self-conscious about making errors in front of an actual Basque speaker?