Definition
In chemistry, activation energy is the minimum amount of energy that reactants must absorb before a chemical reaction can occur. Even reactions that release energy overall still need an initial push to break existing bonds before new ones can form.
As a mental model, activation energy describes the upfront cost of starting any change. A project, habit, or relationship may be self-sustaining once underway, but it still demands a concentrated burst of effort to cross the initial barrier. Many worthwhile changes fail not because they are unsustainable, but because nobody supplied the starting energy.
Why it matters
How it works
Reactions stall in a metastable state — stable enough to sit still, but not at the lowest possible energy. The activation barrier is the hump between the current state and a better one. Once enough energy is concentrated to clear the hump, the system rolls forward on its own.
The practical lever is to either concentrate effort into a single decisive push rather than spreading it thinly, or to reduce the barrier itself. Making a task smaller, removing friction, or recruiting a catalyst all lower the activation energy needed so the same modest effort now suffices.