Re: Anxiety prior to conflict?
Everyone (normal) gets an adrenalin dump if they are put in a threatening situation. The trick is to realise it is NOT a threatening situation. If someone is coming towards you to attack, go to meet them, this allows you to get into the depth of a fight before the adrenalin has negative effects. Don't be 'intimidated' into fighting, wait for them to be aggressive (I know sometimes the converse is often more useful, but this prevents you deliberating over what you do). Stand your ground, use 'the fence' (put up your arm to protect your space, if they invade that space, assume the fight has started and let your body do its reactions!)
It may just be a matter of how much time you've been training (not sure how long you've trained), but knowing aikido menatlly is useless, your body has to know it so that you can move and react without the need of your cerebral cortex. In a fight situation (at least from my experience) you are unable to make many (if any) concious decisions.
Maybe run through scenarios in the dojo. The real beauty of aikido is there is no fight/not fighting duality like other martial arts. You don't have to DO something to people, you just defend yourself in a positive matter i.e. with a striking art, as soon as you strike there is no way to produce a peaceable resolution. With aikido you can use gentle nikkyo, ikkyo techniques to nullify the attack (esp. if it is not really a solid aggressive attack, e.g. if it is only a grab or a push). And often it ends up not even turning into a real fight because they give up.
Hope this helps. Trust in yourself and be positive!