I've been drawing for a long time. I draw all types of forms: life, machinery, landscapes, etc. If I have plenty of references I can produce something half way decent even though it is a fairly slow process from using all the references. My brain remembers what objects look like, but when I try to draw from memory, the outcome is pretty bad. I can't seem to develop the muscle memory. What can I do to overcome this ?
Get a sketch pad and take it with you. Draw from real life as often as possible. Feel free to be rough and work on capturing light and shadow and don’t worry about accuracy, that is why they invented cameras.
Try thinking about how those objects work.
You can look at a few diagrams of human anatomy, or when you eat chicken, see how the wings are made up… I just did that today.
For machinery, I think you should draw some basic forms that have personality in them, and then figure how they’d work.
http://www.wikihow.com/Practice-Gesture-Drawing
To draw better, you must read some comics and magazines to study the proportions and shadows. Reading fashion magazines is much better than reading other books because you are able to study how models pose and what their body proportions are like.