Your can change your state of mind or mood easily using the techniques of anchoring. This means you can, for example, stay calm and relaxed whatever other people are doing or however provoking they may be.
While NLP offers you techniques to create a desired anchor (see below), you are also already affected by anchors throughout your life and go into a good mood or a bad one … feel motivated to do one thing or to do another … feel confident and resourceful or the opposite. We are responding to anchors, but we may not know what they are. These anchors have been built up accidentally and some of them can be used in your favor even without knowing any techniques.
So it is worth investigating what resonates with you most. Very often this is connected to you preferred representational system (–> see VAKOG).
Being quite visual, pictures can work as an anchor (background pictures for your computer, a picture in your purse).
E.g. when I feel very tense and would like to get into some state of calmness and having a fresh mind, I like to remember an early morning hike on the Mount Batur in Bali (–> see Sunrise).
If you are (like I am) also a very auditory person, music playlist might help you to get into a desired state. I have playlists for all kinds of moods on my iPhone – one that helps me to be confident when I make a public appearance, one that gets me into a competitive mode when preparing for a tennis match, one to lift me up when I am down or one to calm me down when I am nervous.
For further reading:
https://nlp-mentor.com/nlp-anchoring/
https://trans4mind.com/personal_development/mindMastery/anchoring.htm