You promise yourself you will start running. You buy the shoes, tell three friends, and picture the fitter version of you. Two weeks pass with the shoes still by the door, because "I will run more" never said when, where, or how.
Implementation Intentions is an execution method that turns a vague goal into a specific if-then plan naming exactly when, where, and how you will act. You decide in advance the moment and place that will trigger the action, in the form "When this situation happens, I will do that." The cue does the remembering for you, so the action fires on a trigger instead of waiting on a burst of motivation. The psychologist Peter Gollwitzer developed the method and tested it across hundreds of studies.
A goal tells you the destination and nothing about the turns. In the moment, tired and busy, you still have to decide when to act, and a tired mind often decides not to. An if-then plan makes that decision once, ahead of time, and ties it to a cue you are certain to meet, so willpower has far less to do on the day.
Build the plan in advance, when you are calm and clear. Five steps turn a wish into a trigger.
You want to take a daily vitamin but keep forgetting, because "remember the vitamin" floats loose in your day with nothing to catch it. You write an implementation intention instead: "When I pour my morning coffee, I will take my vitamin." You move the bottle next to the kettle so the cue and the action sit in the same spot.
The next morning, pouring your coffee puts the bottle right in front of you, and you take the vitamin without any effort to remember. Within a week the coffee alone triggers it, and the habit runs on its own. The goal never changed. What changed is that you tied it to a moment that already happens every single day.