Doing a PhD or starting an industrial career? I will finish my Master degree in electrical engineering (in Germany) soon, but at the moment I am quite unsure about my future after that. Quite some of my fellow students just joined the institutes of the university whose professors supervised their Master's Theses. There they will work as assistants of the professor and go for the PhD.
I have to do an industrial internship during the next months to finish my Master. After that, I would have the opportunity to join my institute as PhD candidate as well (I know that because one of my friends already told me that they are looking for staff at the moment).
Now I am stuck with the decision whether to go for a PhD or to start working in the industry. Usually I really enjoy research and solving problems while exploring some new topics, like I did in my Master's Thesis. But when I think back to the time of my thesis, there were several problems and "wrong" results (that partly contradicted theory, like wrong simulations) that caused a lot of frustration. Back then, it took half a year to write my thesis, but a German PhD in engineering will take 5-6 years. To be honest, I was really relieved when this half year of writing the Master's Thesis was over and I achieved to submit a really good thesis.
Another thing that discourages me is the way that scientists seem to work these days: The university/faculty/professor wants you to publish at least one paper during a certain period of time. But that contradicts my vision of science: You should publish papers if you discovered something new or at least relevant in a field of study, not because some schedule tells you to.
My supervisor at work (who has a PhD) told me that you should never go for a PhD just for having the title or having better career options. He said that you should truly enjoy research because those 5 or 6 years will be a very tough and often frustrating time. If you lack the passion of research you should not go for it.
I am quite clueless at the moment. My basic goal in life is to be happy in general, not necessarily obtaining the highest educational degree. I really do not know if I have the frustration tolerance to find joy in these 5-6 years of doing a PhD.

Long story short:
Which advice would you give any Master graduate who is facing the choice of whether he should start an industrial career or go for a PhD? Can you provide some experiences of your time as PhD candidate? Which questions would you see as most important to be answered to make this decision?

Best regards!
Doing a PhD is a wonderful experience. It requires from you to become monomaniacal and obsessive with a very narrow topic in your discipline. There are many highs and many lows while you work on your doctorate. But the motivation should be your very own desire to learn and deeply engage in our discipline. Doing a doctorate for any other reason (e.g. professional opportunity,social status), will not keep you motivated enough -- let alone guarantee professional attainment. If your Master's thesis or your understanding of how academia works ("publish or perish") did not invigorate you to go for a doctorate, I would discourage you from spending your time and effort in pursuing it. Whatever you decide, good luck!