This is because each piece of toast would be cut into 1/3 since there are 3 friends. You Add 1/3 + 1/3 together since there are two pieces of toast this equals 2/6 if you simplify this the answer is still 1/3
When performing, you already have developed your technique and skill in practice sessions. Knowing that you have already mastered the technique and skill should help you to relax.
Through repetition of performances then comes the master of technique.