Thanks for writing this., so much. I am in my mid twenties struggling to find out what i want to do in my life, and I have this passion towards physics since child and hence i quit my job as an analyst(CS undergraduate)and now on the way to pursue my masters in physics, and all the time I get people walking up to me telling that its not worth, the Phd is not worth the time, and despite of all the anxiety and fear i face everyday worrying about the repercussions, I somehow keep myself motivated and positive. But nonetheless, this question runs in my mind, what if i get tired of it all? what if i lose interest suddenly in physics? maybe like after working for 5 years or 10 years. What then? The insight you have provided has given me some confidence. Thank you.