Giving up good position because of studies I earned my Bachelor Degree in Computer Science 5 years ago. From the moment when I have a diploma in my hands, I thought, enough I never return to academia, no matter what happens. I was very keen to start working. 

By the moment I changed few workplaces. I wanted to try all kind of positions that computer science man can get. All my positions were not very interesting. I wouldn't say I became very experienced programmer, I have some experience, but I don't have a field I am good at, and actually I am not too worried about that. The main problem I think is I don't feel that I do something useful or something challenging, actually, I feel that I waste my time. I do my job, but I don't feel I contribute to myself.

Few years ago I realized that may be it's worth returning to academy. Simply, just because I remember it wasn't boring. I sent few application letters to few good universities in my country, but they didn't apply me. There were universities that just refused without any explanation, and in few of them I fault in interview. 

In this situation, I decide if no official program is allowed, I can just take few courses of Master Degree in any university. The result of my first course was very terrible, I think I was the worsen student on the course. But afterward there was a gradually improvement in the grades (I never took the same course twice). This year again I sent few application letters with my grades, and I was applied by all universities. 

The problem is by now I have a very good position in very successful start-up company. The position is very hard and almost all the time in the office I am under a high pressure, but of course, there are benefits of a successful start-up company, fast promotion, investment, but still I have a feeling that I am doing something wrong.

I don't have a decision yet, either postpone my studies or give up good position. Have you found yourself in a similar situation, when you have give up a lot, just because you want to do something you was dreaming about? Particularly, have you gave up you job for studies, and do you regret about your decision?

tl;dnr: A few years ago, I didn't like my computer programming job.  I was good enough at it, but the job wasn't very challenging and didn't offer much room for personal growth.  I felt like I was wasting my time. Even though I had sworn that I never would, I applied to grad school.  I was not accepted as a full-time student, so I just started taking classes as a non-degree student.  Initially I did badly, but over a few years I improved.  Recently, I was admitted to grad school.  But by now I have a great job in a fast-paced startup.  So I'm torn about whether to quit my job to return to school.  What do you suggest?
An important consideration is "window of opportunity".  How long will you have the chance to go back to school?  Will the school be happy to let you defer for a year?  In contrast, if you leave your current job for school, is there a good chance that you could return to work there after you finish a masters degree?  

Also ask "What are my long-term goals?"  It sounds like you mainly want to be challenged and experience personal growth; perhaps also to "do something useful".  Do you have others long-term goals?  How likely are you to be happy and on your way to these goals in 5 or 10 years if you stay at your current job.  Grad school can be fun, but it's often just a way to delay "real life" for a few years.  If you get a masters, will that really help you to be happier with your life and where you're headed 5 or 10 years after you finish school?