die Beherrschung
self-control
The ability to control one's own feelings, impulses, and reactions and not lose one's composure.
Trotz der Provokation bewahrte er die Beherrschung.
Despite the provocation, he kept his self-control.

self-control / mastery / control
Loading your saved state.
self-control
The ability to control one's own feelings, impulses, and reactions and not lose one's composure.
Trotz der Provokation bewahrte er die Beherrschung.
Despite the provocation, he kept his self-control.

The word is derived from the verb 'beherrschen' (to master/control), which goes back to 'der Herr' (master, lord). The basic idea is therefore to be 'Herr zu sein' (to be master) over something or over yourself, meaning to have full control.
Ein guter Redner beherrscht seine Stimme und seine Nerven.
A good speaker controls his voice and his nerves.
In connection with self-control, 'Beherrschung' (self-control) is often used in fixed expressions. The most common are 'die Beherrschung verlieren' (to lose control), 'die Beherrschung bewahren' (to keep one's composure), and 'die Beherrschung wiedererlangen' (to regain control).
Er war so wütend, dass er die Beherrschung verlor.
He was so angry that he lost control.
To express what someone has mastered, the genitive is usually used. Alternatively, the construction with 'von' + dative is also possible, but the genitive often sounds more elegant.
Die Beherrschung der deutschen Grammatik ist nicht einfach.
Mastery of German grammar is not easy.
When it comes to skills, 'Beherrschung' (mastery) is often combined with adjectives like 'perfekt' (perfect) or 'sicher' (confident/solid). Typical objects are 'eine Sprache' (a language), 'ein Instrument' (an instrument), 'eine Technik' (a technique), or 'ein Handwerk' (a craft).
Für diesen Job ist die sichere Beherrschung von Excel erforderlich.
Confident mastery of Excel is required for this job.
In this meaning, 'Beherrschung' (control) is mostly used in a political, strategic, or military context. It is about control over geographic spaces or people.
Die militärische Beherrschung der Insel war von großer Bedeutung.
Military control of the island was of great importance.
violence / authority / force
'sich in der Gewalt haben' and 'Beherrschung' both describe someone controlling their feelings and reactions. The difference is in the form: 'sich in der Gewalt haben' is a fixed expression with a verb and often sounds somewhat figurative. 'Beherrschung' is a noun and works well in sentences like 'die Beherrschung verlieren' (to lose one's self-control) or 'Beherrschung zeigen' (to show self-control). Learners may confuse them because both refer to control over oneself. In practical terms: you have yourself under control, or you show self-control.

Nach der unfreundlichen Bemerkung verlor sie kurz die Beherrschung.
After the rude comment, she briefly lost her self-control.
Obwohl er sehr wütend war, hatte er sich in der Gewalt.
Although he was very angry, he kept himself under control.