It's not always easy to understand that sometimes, our energy levels vary from day to day and how our mind and body can take a certain amount of energy to use. In a fantasy world, your energy is constantly boundless, you can't get tired and you channel your energy anyway you want but in the real world, energy varies with certain people and it's never equal. Some days, your energy isn't always there and you force your body to keep going because there are responsibilities, things have to be done and you just have to suck it up; it can be draining as fuck. Other days, everything is there, the energy is just crazy and you can go and do many things with ease and just hit the right spots, we've all had some of those days.
I can be very energetic at times like during my training or being out with people, living it up and working on projects or doing certain things like snow shoveling, moving furniture or going on hikes. Sometimes, my energy just isn't there, even if I am training and use up what I can to get through it. I may not always feel up to things and weather affects me sometimes, mental drainage happens and not always in the best place. It's called being human and you do what you can on a day to day basis. Our mental capacity, our physical energy and effort does have limits and some just can't grasp the idea that there's no such thing as the perfect level of energy.
You can take all the pills, the energy drinks, the coffee, the pre-workout you want but eventually, certain things will happen and something will either kill you or put you in the hospital because you overwhelmed the system and the body needs time to heal. We forget that at times and we then run on fumes while making as much effort as possible and sacrificing ourselves to make certain things happen or getting this project done, making sure the kids are ok and if all the bills are paid; we sacrifice the energy we do have in order to fulfil certain tasks in life. In tough times, it can be difficult to have great energy because you have busted your ass with very little reward and your beating up the body in order to make life better for others such as a family, can't get any more real than that.
Is it possible to have more days with great energy than others? Very much so but it's more of an individual thing than just a general spreadsheet of how to incorporate your energy levels. In some cases, having a booster can do the trick like for some a 5 hour energy drink kicks in and you got into that level of being in the zone. Music can help too especially if it helps get into a rhythm to make things flow and your tasks become a little easier. Some people only have a specific type of energy due to brain chemistry and use it to pay attention to certain things because of what requires their time and capacity. For example, there are people with immense brain power like Mathematicians, Engineers, Physicists, those who have the energy and strength to solve equations with great focus; others like Laborers, Athletes, Farmers and Construction Workers who have the brains to channel into their physical body to do great tasks that do take up a ton of energy and use that body to move things, have the ability to operate machinery and control themselves as best as possible so they don't get hurt in order to make a living.
Now, when you mix two styles of energy together, it can have 50-50 or more/less of consequences with the tasks you are given to do and using energy to get those tasks done. You won't see many physicists trying to move furniture or dig ditches for hours on end because not only do they not have the physical capabilities to channel that energy, many don't have the strength or the mental aspect to do those tasks. You're also not going to see much of a Laborer trying to keep up with the science and mathematic mind of a Neil Degrasse Tyson or Stephen Hawking because they don't have the capacity or specific energy and focus to do those things (unless there's a Will Hunting out there somewhere which can be possible). There's also the ability to channel the energy we need to do things even through we are exhausted and letting the tank run even though it's about to be empty. That happens a lot in life especially those who work hard for a living in order to build a life for themselves or raising a family. We channel what is possible through mind over matter and screw the consequences later.
All in all, we do what is possible for us to use the energy we have on any given day. Sometimes we have to go the extra mile and suffer in order to get things done, other times our energy is so big that we have sharper focus and physical capabilities that we didn't think we had, tasks get done with ease and we just feel great and feel invincible. Realistically, we can only do so much and many suffer damage to years of being worn down through physical injuries, mental breakdowns, trying to ease pain with party favors and drinking among other things. Very, very few come out of it without ego or able to heal up certain aspects of damage whether mental, physical, emotional or all three. There's pride in how we use our energy and the outcome of it but there's also ego in the case where you force energy levels and there's no consequences or very little so you push on and things will be alright, that's an extremely rare thing.
Make your energy count and use it as best as you can regardless of the situation but also remember that our energy will only go so far until it becomes crucial.