Don’t Fear the Dark Side

Welcome to Effective Habits, a weekly newsletter where I share evidence-based strategies and tools to help you live a happy, healthy, and productive life.

Today at a Glance:

• Embrace Your Dark Side: A New Perspective on Negative Emotions

• A New Theory on What Limits Our Maximal Aerobic Capacity

• The Zone 2 Practice Session for Public Speaking

Embrace Your Dark Side: A New Perspective on Negative Emotions
Dr. Ethan Kross

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Negative emotions have long been seen as threats to happiness, from ancient religious teachings to modern self-help advice. But growing scientific insight suggests they play a vital role in our well-being. Emotions like anger, envy, or sadness aren’t flaws—they’re signals, evolved to help us navigate life safely and meaningfully. While history is full of extreme efforts to suppress these feelings, from trepanation to lobotomies, today’s research encourages a shift: rather than avoiding discomfort, we can learn to work with it. Managing emotions isn’t about eliminating them, but understanding them and using the right tools to shift between emotional states.

Action!

1. Acknowledge and accept all emotions – Don’t avoid negative feelings or chase only positive ones. Instead, allow yourself to experience emotions fully, learn from them, and shift to another emotional state as needed.

2. Experiment with and find the tools that work for you – There’s no one-size-fits-all solution. Try different strategies, track what helps, and adjust over time. Emotional tools are personal and may change as you do. Some tools to get you started:

   1. Reframing – Shift how you interpret a situation. For example, see failure not as proof you're inadequate but as a challenge and learning opportunity.

   2. Changing your environment – Move to a different physical space (like a quiet park or cozy café) to help reset your emotional state.

   3. Engaging your senses – Use sensory experiences (like listening to your favorite music, smelling something familiar, or savoring a comforting food) to shift your mood.

   4. Journaling – Write about your thoughts and feelings to process and gain clarity on what’s going on internally.

   5. Avoidance (used wisely) – Sometimes, letting go of a thought or situation instead of repeatedly rehashing it can be the healthier choice.

3. Use emotions to guide—not control—you – When you understand the small internal shifts that influence how you feel, you gain the power to steer your mood and mindset more intentionally.

A New Theory on What Limits Our Maximal Aerobic Capacity
Brady Holmer

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Why doesn’t our max heart rate increase as you get fitter? A new review by Ilkka Heinonen sheds light on this puzzle, revealing that the heart’s ability to pump more blood during exercise—key to increasing VO₂ max—comes not from beating faster, but from beating stronger. While stroke volume (how much blood is pumped per beat) rises with training, maximal heart rate stays the same—or even drops—because because pumping faster would reduce the heart’s filling time, limiting its own blood supply and risking oxygen deprivation. Heinonen proposes that sensory nerves in the heart act as internal safeguards, capping heart rate to prevent oxygen shortages in the cardiac muscle. So rather than speeding up, the endurance-trained heart grows larger, increasing stroke volume and optimizing oxygen use. It’s a powerful example of how the body prioritizes efficiency over brute force—building endurance not by pushing harder, but by adapting smarter.

Action!

• Focus your training on rhythmic, low- to moderate-intensity endurance exercises (like Zone 2 cardio) that maximize stroke volume by stretching the heart maximally for extended periods of time. Mix in higher-intensity intervals to challenge the heart further. (This also means that resistance training is a poor way of improving VO₂ max).

The Zone 2 Practice Session for Public Speaking
Sahil Bloom

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Many people struggle with nerves before public speaking, often experiencing a racing heart, quickened breath, and a sense of discomfort that can throw off their delivery. One simple and surprisingly effective way to prepare is to practice your speech while doing light cardio—keeping your heart rate in the Zone 2 range—to simulate the physical state you’ll likely be in when speaking under pressure. This approach helps align your practice conditions with the real experience, making it easier to stay composed when it counts.

Action!

• Practice your speech with an elevated heart rate (e.g., while brisk walking, slow jogging, or cycling). Elevating your heart rate to a moderate level (~Zone 2) in this way conditions you to stay focused and deliver effectively even when your body feels the physical effects of nerves.

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FUN FACT

Bananas are radioactive. Due to being rich in potassium, every banana is actually slightly radioactive thanks to containing the natural isotope potassium-40. Interestingly, your body contains around 16mg of potassium-40, meaning you’re around 280 times more radioactive than a banana already. Any excess potassium-40 you gain from a banana is excreted out within a few hours.

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Disclaimer: The information provided in this newsletter is for informational purposes only and is not intended as medical advice. Please consult a medical professional for advice, diagnosis, or treatment. We are not liable for any risks or issues that may arise from using this information.