Make up your mind beforehand

When you are put under pressure that is not the time to decide how you will react or behave.  Athletes know this.  The reason some people are so clutch is they have practiced so much and decided how they will respond under pressure.  Jesus taught this to His disciples in Luke 21.  He told the disciples in Luke 21:14:

But make up your mind not to worry beforehand how you will defend yourselves.

The time to decide how you will act is before it happens.