In my thirties, I was so consumed with career that I let my health go, I was very overweight, didn't exercise and just put all my focus into work and getting ahead. I developed all types of health problems and pictures of me from that time look like a fat old baby with a beard. It didn't help that I was still wearing clothes from the 90's. Quite embarrassing and I keep pictures from that era buried deep deep below the earth's mantle :)
At age 40, I was recently out of a long-term relationship and moved to a new place and decided to get my health in order. I fixed my diet, started working out, updated my wardrobe, prioritized sleep, etc.
Over the next year, I dropped the extra weight, put on quite a bit of muscle, dressed for the correct era, and overall re-made myself.
A nice surprise was that losing weight and getting in shape resolved nearly all my health issues. I felt like I was in my twenties again - which was a small miracle since I felt like I was a senior citizen in my thirties.
Naturally, my mood and confidence improved. I was dating again, and quickly realized that sexiness-gap is much more of a factor than age-gap. If there's no age-gap, but you're waaaay less sexy than someone else, society will have a problem with it. But even if there's a large age gap, and you are both at similar levels of "sexy", then society accepts it quite readily. Not saying that is good or bad - it's just how our modern society seems to be and was something surprising to me.
Here are some things that helped me:
* Set the barrier to working out as low as possible. I used resistance-bands at home. It's surprising how much muscle you can put on with resistance-bands. Set yourself up for success - it's a much lower hurdle to working out if you can just roll out of bed and workout in your underwear while listening to music/audiobook/etc. You can get super heavy-duty bands that even bodybuilders will struggle with - so don't think you have to go to the gym to put on significant muscle. You don't need to make a big financial investment here - your muscles will grow when working against significant resistance and they don't really care how they get it - just that they get it in sufficient volume and consistency.
* Ignore fad diets and follow only science/evidence based programs. The best I've found are "Renaissance Periodization" and Jeff Nippard. You want to follow those who are non-religious about any particular approach and willing to adjust their approach purely based on the best studies. I wasted soooo much time following crazy diets and fad workouts before I found good reliable data to work with, and that made all the difference.
* Focus on the 99% that matters for diet and exercise. The essentials are very simple. But if you're looking for info on youtube and other places, the majority of videos/articles are focusing on optimizing the 1%. So you can waste a lot of time worrying about the 1% that matters very little and miss the 99% that matters immensely. Remember that fitness experts often get bored of focusing on the basics and will want to constantly explore the exotic fringes. Ignore the exotic fringes - they will be a huge waste of your time unless you are an elite athlete competing in world-class competitions.
* Track what you eat in a calorie/macro counter app - at least until you get reliable intuition about it. I resisted this for a long time, but when I finally did it, I realized that my diet was insane. I was 900 calories one day and 4000 calories another day. My intuition about food and calories was terrible. It wasn't until I started counting calories that I realized what was what. Figuring out my maintenance calories also helped me to keep my energy levels more constant (my 900 calorie days were, non-surprisingly, the days I felt like a wet bag of sand).
* For style, I found Pinterest to be a surprisingly good resource. If you find a style you like that is contemporary and works well for your age, body-type, etc, then you can find thousands of photos that provide good examples. Save all the ones you like and then go through them and look for patterns. Pay attention to colors, fit, etc. Start replacing your current wardrobe with the most common items that work well in the pictures. Observe what is working for others that are similar to you, and start modeling your style after them. This may feel a bit "vain" - but remember, you're not doing anyone any favors by showing up in poor style - do it for others if that helps you overcome that mental hurdle.
* Be patient and gentle with yourself. Taking a note from the parent article: If you notice your dog got fat and out of shape, would you whip him and shame him, or gently encourage him and make it fun to exercise? Treat yourself at least as good as a dog you love. This will take time. The changes will be extremely subtle in the short-term, but will make a big difference long-term. Loving your inner animal will ensure it goes as fast as possible. Shaming or punishing your inner animal will only slow things down and cause you to resent the process. Be creative - make it fun - only boring people get bored.
Most people let themselves atrophy as they age - so you may be surrounded by bad examples that will depress you about aging. Focus instead on the examples of people who are active, growing, and living amazing lives well into their 80's. Then the future of aging won't seem so dark.