Being fit and healthy is not an overly complex problem that needs to be figured out. It's an execution problem for most people and if you can nail down this list of 5 main areas I guarantee your Fitness improves.
Intense Exercise
I know most lists and experts will put Diet as number 1, 2 and 3 but I simply do not believe it is number 1 if you want to be really fit. For me the most important element is Intense Exercise. Whether this is running, cycling, lifting weights, crossfit, swimming, etc etc. For basic health, sure, diet is probably number one. But if you want to be Fit? With Muscles that pop or among the elite in any fitness endeavor within your peers (marathon, crossfit, powerlift, cycling), intense exercise trumps all.
PRs: I measure intensity very simply. Are you regularly setting PRs? Run/Cycle X miles for less time. Bench Press X weight for Y reps, if both X and Y regularly go up, you are likely putting in proper intensity.
Endorphins: the endorphins I get from an intense session are what puts this one over the top for me. If I break a PR in my Bench or Pull ups, I am happier. If I beat my best time for a specific route on my handcyle, I am happier. And typically happier for hours. The satisfaction that results from a great workout carries me though my day.
Diet
So I didn't go off the rails and put diet at the bottom of the list but I think people can put too much emphasis on diet and it leads to more stress. My simple diet Dos and Don'ts.
Don't eat shit. Chips, Soda, Ice Cream, Fast food. If these items are in your diet more than occassionally, you may be eating like shit.
Do Loosely Track Macros/Calories. Get enough protein, around .75 grams per lb of bodyweight. Monitor your carb intake, but do not obsess. Be aware.
Don't Obsess over Macros/Calories. Unless you are entering a physique competition, obessessing over macros and calories just leads to misery. I use to stop and tabulate every single calorie after every meal. This is miserable. Be aware of your macros and calories in general.
Enjoy What You Eat! Find healthy variations that you love. You love burgers? Great, go with the lean hamburger and you are good to go. There is a way to not eat shit AND enjoy what you eat. If you cannot find that balance then you will struggle. Cheat meals where you throw caution to the wind and just enjoy your damn meal are fine, but not more than a couple per week. Or else you will be eating like shit. Force feeding chicken down your throat may be techincally healthy according to calories and macros, but it is miserable if you can’t stand chicken.
Sleep
Sleep and Diet can be interchanged. Both are critical to a healthy lifestyle. If you neglect either, over time, it will catch up with you. If you are under 7 hours per night, fix it. Fast. Chronic lack of sleep will destroy any physical progress you attempt to make via exercise and diet.
Sun
Just getting outside in general is very important. Humans were not made to be stuck inside all day, everyday. Only when shelter was required. Nearly all of our jobs force us inside a building or car for 10 hours per day. Then netflix and video games have us inside every free hour. Get outside. Get some sun. It will improve your mood, skin and sleep.
Walks/Active Recovery
Active recovery is a big thing for people that work out intensely. For myself, I often did intense workouts 5 times per week but nothing in an active recovery state. Going for walks falls into this category. Same with playing with your kids. Basically anything that requires movement but you aren't really tracking anything, beating any PRs. Walks are probably the best form of this since it tackles numerous needs. Active Recovery is critical for mental and physical health. Its movement without stress, which can burn off some extra calories as well as improve your mental state.
It gets you outside so you can breathe some fresh air and get some sun.
It allows you time with your Dog or Spouse, which helps your mental health and relationships.
It gets you off your damn phone and off Social Media. After work, Social Media is likely the biggest stress causer in your life. How often are you in a fine mood, then in 10 minutes of looking through your Twitter feed you come across something that annoys or downright pisses you off? Social media is a sesspool these days and IMO is better just left ignored for many people. People showing off their Life Highlights, Trolling, Politics, Sports Takes, etc. Actively track one weeks worth of social media use. How often did you feel better after 10 minutes vs feeling worse? If you feel worse more than you feel better, get off it forever.
Are you lacking in any of these areas? If you are truly lacking in the first three than fitness is not a priority in your life so you can stop reading now. These first three are absolutely critical to being Fit. But the last two are underrated items that can help complete your puzzle. Your body craves sunlight. I guarantee your skin will improve along with your sleep if you can carve out at least 30minutes per day of sun. I know this can be VERY tough with some work schedules, but do what you can. Along with the importance of sun, active recovery is critical for your body and mind. If the only movement you do is HIGH intensity exercise you will likely run into ligament problems, muscle tears, etc. Active recovery helps keep the juices flowing throughout the body and the mind.