So you're here after completing your first year of Ph.D. in Theoretical Physics (in India) and your second year of Ph.D. in Theoretical Physics (in India)? Bravo!
What's more - you now actually know what you're going to do over the next few years. With your thesis proposal in more-or-less a shape, and concrete ideas starting to develop, this is going to be an exciting year; a very different one too, with its own set of quirks and challenges.
What would feel really strange at first, and you'll be realizing this in sudden flashes, is that you will now be able to converse in "scientific - lingo". Soon you'll realize that the things you're saying, or understanding, are in a world of their own, and before you know it, non-scientist people around you will give you looks that you once used to give to someone more mature in the field when they talked about their work. This is not bad. This is very good. It means you've matured as a researcher. But alas! There are always two sides of a (fair and normal) coin.
This increased maturity will be crippling you with overwhelming influx of knowledge of the field you're working on. Soon you will be rid of a fear of reading academic papers, and a mere glance at once would enable you to "roughly" pick up its contents. But then you start going down a rabbit hole, reading one reference after the other, going deeper and deeper all the way decades back, only to realize that the breakthrough ideas in your mind have been broken through even before you came into existence. Well, barring that, you will be overwhelmed with the sheer amount of reading itself. And trust me, it gets addicting. Unfortunately, you can't read everything. There is just too much, even if you're only limited to your own specific field of study.
You might then say, well, I came into this line of work to learn, to gain knowledge, and all that. So if I am being able to read technical stuff, and know more and more, this is heaven! But unlike actual heaven (if one exists), this heaven is not forever; membership of this heaven requires you to make actual scientific contributions. So then you start creating problems to solve, check whether they've already been solved, and then get to work. Turns out, working on solving a problem, despite being hard and uncertain, takes a lot of mental focus; and time. So what would end up happening is while trying to solve a problem, you get stuck, go and read things that would help you get un-stuck, then start working again, and then get stuck again, and then look-up what you need to get un-stuck, and start working again. This is ideal. The problem only arises when you take these necessary breaks from working to go and read. You will feel this constant naggin behind the back of your head that you need to work on the project you're working on, and it'l stop you from continuing reading. Which is a good thing it seems. But then when you get back to work, you feel this incessant pinging from your heart telling you that what you were reading, didn't make complete sense to you (although it was enough to get started on working again), and you'd want to go back and go down references after references trying to quench your thirst of knowledge (threw in these big words for a dramatic effect).
It would become a constant struggle between working and studying: the former necessary for survival, the latter necessary for survival, with the difference in suvivalities being physical vs mental. The good news, however, is you'd soon get used to it, and will learn to manage both efficiently. But, it is going to be really hard. Most lose focus, most get frustrated, most lose their way and their original motivation for coming to do a Ph.D. in fundamental sciences. But if you power through it, you'll soon feel all the original reasons making sense again. Just. Hang. On. And of course, read, read, read, and work and work and work.
Before I end, and this may seem contradictory to the "grinding" mindset required during a Ph.D., I strongly advise you take breaks. Many quitters had simply burned-out in this period of to-and-fro between just work and study. Don't abandon your roots, don't abandon that love of literature, or art, or music. Or of news, politics, or social issues. As much as obtaining a Ph.D. is important, it isn't going to count at the other end if you are clueless about everything else in this singular existence of yours. The trick is to maintain a sweet balance, and that indeed is hard. Complicated science stuff, or math, or coding doesn't make a Ph.D. difficult. These things do. All in all, it'll be a good year, and at the end of it, you'll be looking at a very different version of yourself, a version that now would believe that it could actually become a scientist; finally believing in the answer that your younger self used to so naively tell elders when asked, "what do you want to become when you grow up?".