You haven’t done anything wrong but different choices lead to different lifestyles.
Some pick their studies based on career progression and earning potentials rather than passion and other pick their studies based on what they would like to do even if it means a lower salary/worse schedule.
While nursing is a really important and rewarding job, I assume one knows choosing it that they won’t earn a lawyer or tech salary and that it will be more mentally/physically challenging (difficult patients/long shifts etc…).
If your friend picked studies or jobs with career progression and a natural salary progression then they were always going to be better off than you.
Also very few people make financial decisions in an order that makes sense.
The logical thing would be to save up for a house first (while your earning potential is not affected by childcare and children’s costs) and then have kids, same, if your goal is to save for a house/car, then ideally prioritizing that over several holidays a year.
Most people do things in the order of what appeals most to them (having children /holidaying) and then are surprised that their friends who had kids later in life have a house and the means to offer a different experience to their kids.
I will give you an example of my own to highlight what I say , because while we are in a different age group (17 years difference between us so she is in her 40’s while I am starting my 30’s) my mother and I are in the same industry but have completely different lives and finances and financial mindset despite her technically having been born in the better financial era and it’s her way of doing things that has made me make completely different choices for myself.
My mom chose to have 4 kids before 30 (5 now) and 3 before her mid twenties, therefore sacrificing her ability to study or have a career with potential, she did buy eventually at 29 before the birth of her 4th child but had to move to the country side and still struggle to pay off the mortgage 20 years later and now have health issue which now means she can’t work in the industry anymore and need to reconvert (how she will do that without losing the ability to pay her mortgage is a mystery). She has also never had a decent car because due to the amount of kids always needed a 7 seaters and they are expensive so she would buy the cheapest one (and likely spent more trying to keep it on the road that a decent car would have costed). All in all she is in a terrible financial position and at an age where she should be able to start relaxing as almost all of her kids are adults she is actually going to have to stress more regarding the basics.
Personally, I have never understood my mom’s choices and vowed to do things differently and as a result live a completely different life. I work in the same industry as her and actually started at a much lower salary than her but, because I don’t have kids I was able to take positions that she was never in a position to take. As a result I make 5 times her salary and because I don’t have kids I am able to save a lot and while at 30, she had 4 kids, at 30 I have none but do have 2 properties (one paid outright and the other one rented out that pays for itself), and yet despite my money I live frugally, have an old car 2008, my phone is almost 4 years old, I do allow myself some luxury like traveling but don’t fritter it in unnecessary upgrades when I do and do it on the cheap as much as possible.
I am planing my finances so as to be able to have and offer the life I want to my future kids before I even have them and in parallel saving so I can retire early or at least work only 3 months a year once they are born, because I am aware that having a child will impact my ability to work and my earning potential (my career not being really compatible with family life or at least not at my pay bracket).
if I had listened to my heart I would already have kids, but I am glad I don’t because I now have the ability to provide them with a massive step up I have never had when I was a kid (or even young adult), and it brings me comfort to know that if I do have children then money won’t be a stress factor because I do remember what it’s like to grow up in an environment where my parents made the choice to have kids first and to figure it out later and having to go without and money being a continuous source of stress.
So I think personal choices and the order in which you do things and what you prioritize are often the main source of what leads to one person having a certain lifestyle vs the other. Financial independence was more important to me than having children for example so I will always lead a different life to someone who is making the opposite choice and is willing to sacrifice their financial independence for the benefits of having children.
So if you want different results, OP, look at what you can change or are willing to sacrifice to make it happen (less to no holidays? Less time with your family but more working hours and more pay? A career that you hate but pay better?) most choices come at a cost. You can’t always see it from outside.