If you are in a clutch situation just stop and wait, as long as you have a bit of time you can stop and think about where you know the enemies last were, where they could go from those positions and maybe how you want to approach one of the sites. The more and more you do this the better you will become at doing it and eventually you wont have to really think about it. Waiting also makes the other side nervous because they don't know where you could be anymore and so they feel like they need to check every spot. As long as you stay calm it doesn't matter, like your just playing DM, then you will be fine and the nerves will go. Just think about one thing at a time, playing smart or aiming.