Why did I desperately pursue a chance to obtain my PhD, only to ultimately turn down the offer?

"I don't think it is possible that you can do it in a short time." After the first interview, the professor left this feedback. Apparently, he was seriously worried about my non-computer-science background and gave me a list of courses that I missed as a communication engineering student.

"Well, I am not sure about your coding ability so I'll give you a project to see how you react to that." The professor gave me estimated finish hours, "Beyond that, this might be too complex for you and we did not suggest you forward the application." It is surely complex for me, given that I spent two days out of seven days just understanding the email--what the prof. want me to do? However, I was so determined that no matter what I'll take this down.

With the other three projects undergoing for the whole month, I desperately squeezed my time and spirits to get the two mini-projects that the professor assigned to me sequentially. During the one week for each of them, I slept only 3 hours a day, doing the project all the rest of my days.

"You positively impressed us with your coding and essays." He finally said.

I am so moved inside that my endeavor had a result, however, when I had to decide whether I would love to give the rest of my life toward this edge, I hesitated. My feelings changed along the projects, and I started to consider what is the point of pursuing this PhD. I searched the reason people pursue a PhD, what they get from it, and whether they suggest they have that. A persuasive answer finally made up my mind:

"A PhD is someone to whom society allocates resources to push the boundaries of human knowledge. Without a strong passion for their field and a willingness to devote their attention and spare time to explore its uncertainties, this pursuit can become exhaustive and meaningless. ” PhD is more than a title that people respect, and more than the reputation and merits it might continuously get, it is also about passion and responsibility toward human good.

"Am I? " Am I that passionate about this field? Surely I am more into computer programming than signal processing but I still find this different from what I want to do. Also, my feelings would not lie——while I do these projects I feel a little burned out. It was a good chance though, however, it seemed that it was just not that really for me.

With this determination in mind, I wrote an email to share my sincere sorry that I have to end this progress.