Defence

In the infamous neverending debate between the so-called tactical player ("muh 99% tactics") and the so-called positional player ("muh tactics flow from superior position") most people overlook that the purpose of tactics is far from exclusively pulling off some fancy finishing move.

Being able to calculate good moves available to your opponent is a critical skill in order to survive and when you have to do that, sometimes you don't have the better position at all!!

How do you, in the diagram below, avoid leaving the tournament room in tears as white?

You're talking about calculations. The ability to calculate moves is important for both types of players. But the difference between tactical player and positional player is: tactical player wants to attack the king, he appreciates open positions and he wants to bring complications; positional player likes closed positions, he likes to have a slight but stable advantage in the opening instead of crazy attack for the sacrificed pawn and so forth and so on... Being unable to calculate variations doesn't mean that someone is "positional player".