Before you dive into scribbling everywhere, you need a game plan
Make sort of a map on your page where you measure things, relate features with plumb lines, angles, and horizontals, and map out your forms. Once your ready and your page looks like a schematic, put your values down with big brushes while keeping lighting direction and form in mind, gradually reduces brush size as you define more intricate features.
As you said, you need to take your time. Drawing is a step by step process that you have to think about, the people that dive in and start scribbling everywhere based on intuition for hours are the people that end up with shitty drawings that make no sense. Every mark has a purpose, no more scribbling.
Also, move on, no sense in continuing on with this peice, start a new one. If i squint my eyes at your picture, it kinda makes sense, so you probably got some potential.