In this article written by MyFitness Pal, multiple dietitians come together to discuss the most important aspects of successful and long term diet/lifestyle changes.
It is so easy to get caught up on every minuscule detail of eating healthy, serving sizes, calorie intake, and macronutrient distribution. In general, as long as you're making more healthy diet changes than you previously were, you're headed in the right direction.
Make sure these changes are sustainable and that you'll be able to keep up with these goals and changes for the rest of your life. Therefore, think about these goals before putting them to paper.
For example, getting started with physical activity: even if it's a goal for a few minutes every day sounds a lot more realistic than going from no regular activity to one hour every day.
There is no need to focus in on every aspect of eating "perfectly" when you can identify a few small but significant things to work on; try taking a big picture, or "big rock" approach!
Here is a link to the full article: https://blog.myfitnesspal.com/the-big-rocks-that-make-a-difference-for-weight-loss/