I recently watched Sam Oven’s video which provides a great answer to this question.
You can’t do the work because you don’t love what you do.
It’s simple: if you love what you do, you will work on your thing six days a week, twelve hours a day, year after year.
I know it sounds so obvious but that doesn’t make it less true. If you (like most people) don’t love your work, you always must force yourself to do it. This drains your energy and willpower.
Your willpower is limited.
A famous psychological study argues that “A growing body of research shows that resisting repeated temptations takes a mental toll. Some experts liken willpower to a muscle that can get fatigued from overuse.” 
Now, have a look at your YouTube search history. Can you identify certain patterns? Is it hard for you to consume content about the areas you love?
But it certainly is difficult to consume content which you find boring and which doesn’t interest you.
Today, everyone can create a niche website focusing on just the area they like most. This is the strategy of the founders of incomeschool: create small niche sites with valuable content in your passion area. Those guys enjoy massive success with their strategy.
It’s really simple to create content, write blog articles, or shoot videos about the topics you love.
My wife makes fun of me because I won’t stop talking about my Finxter business. A friend of mine can talk about electronic music forever. My uncle doesn’t stop talking about Roman history.
What is it YOU are talking about all the time?
You can create a niche business online doing just that: talk about the thing all the time.
Now, imagine there are two people: one hates and the other loves talking about ‘dog food’. Both set up a website and start their niche site. Based on what you know: who will crush the other one?
Although the answer is obvious, people do not consider it when choosing their job.
I get to work in a job that I love, but I have always worked at a job that I loved. I loved it just as much when I thought it was a big deal to make $-,………. I urge you to work in jobs that you love. I think you are out of your mind if you keep taking jobs that you don’t like because you think it will look good in your resume. I was with a fellow at Harvard the other day who was taking me over to talk. He was -8 and he was telling me all that he had done in life, which was terrific. And then I said, “What will you do next?”, “Well,”, he said, “Maybe after I get my MBA I will go to work for a consulting firm because it will look good on my resume.” I said, “Look, you are -8 and you have been doing all these things, you have a resume -… times than anybody I have ever seen. Isn’t that a little like saving up sex for your old age?”Warren Buffet
Warren Buffet loves his job and see what kind of success he enjoys. Work does not feel like work for him. And this may exactly be the reason WHY he spent so much time working on his investment firm Berkshire.
“There comes a time when you ought to start doing what you want. Take a job that you love. You will jump out of bed in the morning. When I first got out of Columbia Business School, I want to go to work for Graham immediately for nothing. He thought I was over-priced. But I kept pestering him. I sold securities for three years and I kept writing him and finally I went to work for him for a couple of years. It was a great experience. But I always worked in a job that I loved doing. You really should take a job that if you were independently wealthy that would be the job you would take. You will learn something, you will be excited about, and you will jump out of bed. You can’t miss. You may try something else later on, but you will get way more out of it and I don’t care what the starting salary is.”Warren Buffet
To come back to your question: you feel unproductive because you are unproductive…
… and you are unproductive because you need to spend too much energy for every minute you are producing…
… and it costs you energy because you don’t love what you do.
So what to do about it?
Go inside. Spend the day to investigate your search history (YouTube, Google, Amazon). Figure out patterns of what you love to do. Where do you have to spend the least amount of energy when consuming content? And where when producing content? Can you make a business out of it?
Do this today and this may easily be the most productive day in your life.
If you can’t leave your job or profession—why? At least try to mitigate the effects by owning your choice of staying in the profession. It’s your choice so choose your professional goals, write them down every day, become ambitious again, and start dreaming about your success in your job.
If you can’t do even that, quit your job immediately.