The use of the future tense for describing one's usual routines [duplicate]

In both cases will is correctly used. In the first example, will is used to indicate that the doing of a kata is typical behaviour. Swan in Practical English Usage (p629) states:

We can use will to talk about typical behaviour. Example: She'll sit talking to herself for hours.

In the second example, the knowing is in the present and the failing is in the future, so there is no problem in using will:

I know now that at some point in the future I will fail.

English has no future tense. Will + the plain form of the verb can express the future, but it has other functions as well. One of them is to express predictable or habitual behaviour, and that’s what it’s doing in your examples.

For your second point, I'm pretty sure the author uses 'will' because it isn't necessary that the person he's talking about has already failed. Saying:

However, a professional also knows that there are times when he fails, his risk calculations are wrong, his abilities fall short; he looks in the mirror and sees an arrogant fool smiling back at him.

implies that having such incidents is regular; that it happens frequently to a professional. Perhaps the author doesn't want to imply that. It isn't necessary, after all, that a professional must have been through such an incident. He wants to show that although it may not have occured till date, there will be such an unfortunate time when he will fail.