I am 21 years old. I hate my job and I am single. I don't have any savings. There is nothing good in my life. How can I deal with this?

Just because you don't like you job doesn't mean you are stuck there for life.  Start looking for something else in your spare time and be thankful you have a means of meeting your needs for now.

get a better job, start saving money

You should get a dog. They are always there for you as people cannot be.

Realize you are typical and get over it. Most 21-year-olds have nothing. Look for another job while you still have that one. Some 21-year-olds are still dependent on their parents.

Get rid of social media. Stop living a comparative lifestyle subconsciously. Start taking interest in reading interesting things that you like, not just watching videos. You'll find a passion soon enough, instead of worrying about what people think about you, about the girlfriend you don't yet have. When you find your passion, obsess over it, become a master. Find passion, security and real worth for yourself.

Create real value for yourself. Get ready for when you meet your other half, because be realistic, if you met her today would you feel worthy?? In this whole process, you'll feel yourself becoming more and more worthy, to yourself, which is the most important part of this life. Be selfish in that aspect, because if you don't feel worthy to yourself in a real way, your whole world will be unworthy. 

There are still many good things in your life, despite at the moment you do not feel like there are. You have opportunities to change your future and no children to take care of. Also not having any health problems is something that is often taken for granted. Think about what you would like to do in the future. You need something that motivates you enough to get up in the morning. Set some small goals to start with, do not give up, learn from your mistakes and develop as a person. There is also plenty of time for relationships when you are older. For now focus on keeping in touch with your closest friends, but do not forget to make new friendships.

Start training for a job that you would enjoy.  Keep the current job, or any other you can get, long enough to see you through that training and to a better job.

You could set up a savings account. I believe in God, and I pray to Him, especially when I'm unhappy. The good thing about my life is going to church and learning that God is our comforter.

Join the military.

Keep grinding. It's nice to be single if you are a car enthusiast.