The first step in rising to anger, is to note that you are angry, for that is to enter master of the situation, having determined the need of it, and its height, and going no further; with this considered judgment let your wrath wax, and wane.

[El primer paso del apasionarse es advertir que se apasiona, que es entrar con señorío del afecto, tanteando la necesidad hasta tal punto de enojo, y no más. Con esta superior refleja entre y salga en una ira.]

Baltasar Gracián y Morales (1601–1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 155 (1647) [tr. Fischer (1937)]
    (Source)

(Source (Spanish)). Other translations:

The first step to moderation, is to perceive that we are falling into passion. By that means we enter the lists with a full power over our selves, and may examine how far it is necessary to give way to our resentment. With that swaying reflexion, we may be angry, and put a stop to it as we please.
[Flesher ed. (1685)]

The first step towards getting into a passion is to announce that you are in a passion. By this means you begin the conflict with command over your temper, for one has to regulate one's passion to the exact point that is necessary and no further. This is the art of arts in falling into and getting out of a rage.
[tr. Jacobs (1892)]

The first thing to do when you are upset is to notice that you are. You begin by mastering your emotions and determining not to go any further. With this superior sort of caution you can put a quick end to your anger.
[tr. Maurer (1992)]