The chances are your mind will stray from your intention, so choose a mantra that works for you, and repeat it to yourself throughout the day. A positive affirmation can help bring a sense of calm when your stress levels are rising, perhaps after dealing with a challenging customer (try career coach Ashley Stahl's suggestion of: "Peace begins with me"), or when prepping for a presentation (try Ashley's recommendation of: "I am strong, capable, and ready").
You might choose a different mantra each day, or have a favourite you stick with. Pick yours by asking yourself how you want to be in the world, and use the present tense. Keep it in your head, or write it on a post-it note and stick it somewhere you'll see regularly.