Improvement is a slow and often uneven process, you just always gotta recognise your own progress even if it feels like you are still stuck. I would highly recommend using Saint11โs tutorials, they helped me a lot starting out. My list of resources can be found here: Lukeโs Pixel Art Essentials! 
One major thing is that if you ever need to draw something unfamiliar, just take a few secs to google and pull up a reference (we know what something is, but we rarely remember every detail that makes it feel real)
Finally, here are some graphs that I love a lot and help me thru lows
