Critique and advice are very welcome.

I need to practice shading as I have a almost finished piece from half a year ago that I want to finish. These are some mandarins and some other things in my room that I tried to use as practice. I drew lines for the first 3 but after that I just used wide shading strokes to draw the objects and used a smudge stick to make it look cleaner.
I'm not sure if this is THE RIGHT WAY to practice it though, I'm just not sure.
Any advice would be helpful.

I'm sorry for the lack of art from me. I've been working on my Literature Review until mid of August and a few other things came up, but after that I've just been super anxious about drawing again. I keep thinking about all the things I promised and never drew or finished. Whenever I make a attempt to draw all the feelings from everything I've tried and failed come back to haunt me. I'm not sure how to deal with this. I'm not sure how I'm supposed to improve. I feel like I waste my time trying to find the right way but never finding it. How do other artists improve so fast, how?
How do I get there where really great artists got? What am I doing wrong? What is the right way?

I don't know where to start and I don't know how I'm supposed to organize my art practice.