The time it takes to form a habit varies depending on the person, the habit in question, and other factors like motivation, consistency, and environment. However, research provides some insights:

### 1. **The 21-Day Myth**
You’ve probably heard that it takes 21 days to form a habit, but this idea comes from a misinterpretation of Dr. Maxwell Maltz's work. In his 1960 book *Psycho-Cybernetics*, Maltz observed that it took patients about 21 days to adjust to changes such as amputations or cosmetic surgery. Over time, this concept was generalized and simplified, leading to the "21-day rule" for habit formation. However, this is not accurate for most people.

### 2. **The 66-Day Average**
A more reliable study conducted by Dr. Phillippa Lally and her team at University College London found that, on average, it takes **66 days** to form a habit. The study, which followed 96 participants over a 12-week period, showed that the time it took to form a habit varied widely—from **18 days** to **254 days**—depending on the individual and the complexity of the habit.

For example:
- **Simple habits** like drinking a glass of water in the morning were formed more quickly.
- **More complex habits** like exercising regularly took much longer to become automatic.

### 3. **Factors That Affect Habit Formation**
Several factors influence how long it takes to form a habit:

- **Complexity of the habit**: Simple habits (e.g., drinking water) tend to take less time than complex ones (e.g., learning to play an instrument).
- **Consistency**: The more consistently you repeat the habit, the quicker it forms. Missing days or being inconsistent can slow down the process.
- **Environment**: A supportive environment can help reinforce habits. For instance, if your goal is to eat healthier, surrounding yourself with nutritious food makes the habit easier to form.
- **Personal motivation**: If you are highly motivated and committed to a habit, you’re more likely to stick with it long enough to make it automatic.

### 4. **The "Automaticity" Threshold**
The goal of habit formation is to reach the point where the behavior becomes automatic—what researchers call "automaticity." This means you engage in the habit without needing much thought or effort. The 66-day average suggests that, for most habits, about two months of consistent repetition is needed for them to feel automatic.

### 5. **Don’t Stress About Perfection**
The key takeaway is that forming a habit isn’t about hitting an exact number of days. It’s about being **consistent** and **patient**. It’s okay to miss a day or two—Lally’s research found that occasional slips didn’t significantly affect the process as long as people resumed their habit soon after.

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### In Summary:
- **On average, it takes 66 days to form a habit.**
- **Simple habits** can take as little as 18 days, while **more complex habits** can take several months.
- **Consistency** and **patience** are more important than aiming for a specific number of days.

Focus on regular practice, and your habit will gradually solidify over time!