As an oil painter, coloring digitally aggravates me to no end even after years of practice. It's just way easier to mix the right color on a palette for me than to pick one out of the millions on the screen. That said, some things that have helped me are:
1) Creating a limited palette to use before you begin coloring. This keeps you from going overboard with color and helps establish value levels. 2) Establishing values after sketching. If you can set down your dark and light tones before adding color, or getting too far ahead in your composition, the end result will ultimately have better tonal ranges and be less muddy. Also, if you add a medium tone, remember it should be used as a compositional tool rather than used as a shading tool. 3) Using a canvas that is much larger than what the final image will be. Working in a larger canvas will allow you to work more loosely while also allowing for more detail. At the same time, you will eventually fixate less on packing every detail you can think of in an image because, once scaled down, you won't be able to see it. 4) Working around the entire image rather than finishing one area and moving on. This makes sure the whole image looks cohesive and will help keep values in check. 5) Using program filters/tools. While working on an image, I keep a desaturated filter above my layers to turn on and off to check my values (if working in color). When I'm finished, I typically use the curves tool or throw on an overlay color to boost the colors or strengthen the contrast within the image. I don't use Procreate, but I assume there are similar functions in it.
I also second what Aminirus said. I often watch speed paint/timelapse videos either to see a certain artist's workflow or to get myself in the mood to make my own art.
If you have any further questions about what I've suggested, feel free to ask! Also, if you wouldn't mind sharing some of what you've sketched or colored it could really help us provide you with better and more direct feedback