Lack of mental fitness, endurance, health, strength, or brain-power. This is always confused with low energy, when in reality, both have nothing to do with each other.

The single most thing that is holding you back from your ultimate success and having the life that you truly want is easy fatigability.

Fix that, before you try to do anything else first.

Mental exercise, until you feel like you’re dying is the only answer. And you do that consistently over a prolonged period of time, until you feel a difference. 

You can have an abundance of energy, endless energy, and all the energy in the world, but still experience mental fatigue easily and prematurely, and without even having done anything that justifies or explains that fatigue. This is like feeling extremely physically tired, but being unable to sleep.

To understand this, let’s say you have a ton of energy, but your brain is structurally physically weak, so the physical matter of your brain now can no longer run at maximum capacity, even if you feel you still have a lot of energy, and you don’t feel tired at all. An example for this is having an extremely short attention span, despite being well-rested, highly energetic, young and healthy, and not tired at all.

Another example for that is having information overload or a lot on your plate currently, to the extent that you feel like you don’t have the mental space to focus on anything, even though you’re still well-rested and not mentally or physically fatigued at all.

I know that exercise increases your energy levels, and so does sleep and meditation. Also a lot of other things can do so, not the least of which is coffee for example. But all this falls under the category of energy only. This is like talking about how to have more car fuel, as opposed to having a better or superior engine. You need to work on your engine, or else you’ll always overheat or fatigue easily, quickly, and prematurely, even if you have all the fuel in the world.