Many happenings in your 25th year: you are getting married in August and then you are driving to Ann Arbor, Michigan, to start a doctoral program. Of course, you are scared. Remember the advice: “If you are not frightened, you should be frightened that you aren’t.” Knowing you, I suspect you have thought of all the things that might go wrong both in a marriage and in graduate work. You should convince yourself all these bad things will not happen; if you do, they probably will not. Of course, you need to sensibly balance being prepared and being obsessed, and you have the rest of your life to figure out the balance.
Your immediate problem is making a marriage work. You have to ensure that your new wife finds life together fulfilling, that it opens opportunities for her, that she can do more things with you as a partner than without. I think even at 25 you wanted to be a teacher, probably then as a complement to creating things as an engineer. You will be a good teacher if you help students fulfill their promise, if you open opportunities for them, if you make it possible for them to do something they could not.
The upcoming graduate program will be your last—finally the pressure to get admitted to the next institution has diminished. You have more of an opportunity to select what you want to study. Go ahead and do it—focus on what excites you. If the topic is not in academic fashion now, chances are it will be soon. To paraphrase a valid remark: “Being typical sucks.” Another positive aspect of graduate school is that you can concentrate with no campus organizations or rituals to drain your attention. This may be the last time in your life you can fully immerse yourself in thinking about one thing for an appreciable time. It will be exhilarating both to be fully absorbed and to believe you know more about a subject than anyone else in the world. Fun is not only at parties, the golf course, or watching sports. Be a nerd if you like.
Am sorry this letter is pretentious and solemn. What I really want to say is do what you enjoy, build a life with your spouse, and don’t worry. Things will work out—they always have.