If you're looking to make a change in any area of your life, making dramatic 180 degree changes almost never work in the long run.
Most people do this because they want to see results immediately, and don't put any thought into the process. In many cases, these people adapt the "all or nothing" mentality, and go 100% all in.
The downside to going 100% all in and having this mindset is that the second life happens and you're not able to be perfect, it causes an intense level of stress and often makes the person want to quit.
Rather than adapting the all or nothing mindset and being results oriented, the people who are successful long term develop the "progress, not perfection" mindset and are more process oriented.
Nobody on earth has ever done something and not made a mistake. You wouldn't want this to be the case anyway, because mistakes are how you ultimately learn. It's important that we see our "mistakes" as opportunities to learn and grow.
Let's take your nutrition for example. If you have a lot of work to do when it comes to improving your nutrition, and the thought of it alone stresses you out, the key here is to find the EASIEST thing you can do. We like the process of adding good things rather than taking away bad things.
One of the first things we like to work on is adding more protein into your routine. Think of your favorite type of protein (chicken, fish, eggs, etc.), and make it a goal to have some of that food one time per day. If it's your favorite, it should be easy!
Either way, with anything you're trying to change, make sure you start small and value progress over perfection.. nobody is perfect!