Because your goals are not the goals of your brain.
Your brain has the same goal as other animals a million years ago: your safety and procreation.
Everything else is not interesting to your brain.
Motivation and laziness are what society wants from you.
Motivation is the process of forcing yourself when your brain does not want to do something. Laziness is when your brain does not want to do something.
You can motivate with fear, as invaders have done from time immemorial.
You can motivate with shame (when they talk about laziness), this is how they did it from For centuries, those who did not want to look aggressive.
Consciousness is a small part of your brain that is forced to obey the rest of the brain.
It’s not the brain that makes us uncomfortable, we’re doing the stuff.
The brain tries to keep us from stress and destruction when we try to be “productive and efficient.”
The brain is trying to dissuade us from goals that are not worth the effort when we are trying to write to-do lists for the day.
The brain tries to snatch at least a little time to rest when we try to "not sit on social networks and do business ".
True productivity is a delicate, dynamic balance between work and rest.
The brain is not comfortable with idleness and hard work. He needs the right work rhythm, which will put him in a state of flow, and the right management of the body budget. This requires a good understanding of how the brain and body work (well, or mentors who, if something happens, will save you from trouble), and especially - an understanding of your own characteristics.
The majority of productive-effective-self-developing, unfortunately, does not possess. And predictably fails.
Because your brain is not some kind of separate creature that needs to be made to act as you want. Your brain is yourself. And he is cunning just as you are.
Deceiving yourself is a thankless and ineffective endeavor. You seem to be split into two parts. One - correct, smart, purposeful - it's like you, the other - lazy, cunning, trying to evade - it's like your brain (and honestly, who?).
One part constantly thinks that smarter than the other and tries to educate her. The other part, being visually embarrassed, is not going to give in. Internal conflict leads to unpleasant consequences in the form of procrastination, shame, harsh self-criticism.
So the sooner you stop playing Alice in Wonderland, becoming a strict teacher to yourself, the more effective your actions will be.
Why doesn't the "brain" (you) have motivation? Because not every case is interesting and necessary. Why doesn't he act "for the benefit of the ends"? Because he understands that the good is not the same, and the goals are not your own, but imposed.
So listen often to your "lazy brain" (inner voice), it is not as stupid as you want to imagine it.
The brain is not that tricky. We just have many differently directed desires, needs and values at the same time. An attempt to ignore, a volitional effort to neglect some of them leads to an internal conflict: one part of our psyche wants to earn twice as much money as it is now, and writes goals according to SMART criteria. Three other parts of our psyche are not very supportive.
One wants peace, because usually in order to earn at least twice as much as now, it is not enough just to do more diligently what you do. You will have to completely change the course of action, invest resources in training, new activities - and all this without a guarantee of success. Peace !!
The second wants a harmoniously developing personal relationship. To hell with him, with your husband, but at least with your child: time and energy are the resources that a new project will powerfully devour from your relationship. At least the first two or three years (well, I'm here - for an example).
The third - remembers the courses passed six months ago about the fact that you are a Goddess ... slamming at work, this is wrong, it shouldn't be like that, you just have to correctly make a request to the Universe!
The most interesting thing is when a person realizes that part of himself that is about Goal and SMART, and the other three are generally does not hold people: all this nonsense and self-indulgence, it's not me at all, I'm real - here, with a Purpose.
Well, have you tried to press on the gas and the brake at the same time, or chaotically? - I am not a motorist, but I suspect that the result will be very similar to what you describe with your question.
Now you will not be surprised at my advice: you can go to a coach or a consulting psychologist. You can do it yourself - the main key is to sort out all your wants and with yourself - to agree.
P.S. Yes, you understand, of course, that the description of specific parts is an example, there are not necessarily so many of them, and even more so just such)