This is a discussion on How to think under pressure within the online poker forums, in the General Poker section; I'm posting below a link to an excellent BBC article about the impact of incomplete information on the decision making process in both poker and
Take your time on the felt even if impatient opponents are whining that you are using your timebank before acting instead of doing instant actions without thought that you might regret later.
Off the felt plan everything methodically make it as hard as possible for yourself to bust your entire bankroll because that is where the real pressure is.
of course, as usual, it will not work, but over time, or rather with experience, the pressure will not be as strong as before. and of course I will say banality, you need to observe bankroll management and there will be no pressure.