Don't worry about memorising everything you see. Memorize how to draw building blocks - basic cube, sphere, cone etc and then you can build what you want like Lego. Don't be afraid of using reference. The internet/life is a great resource. Use it. Don't put so much pressure on yourself and enjoy the process of drawing :)

You are going through a rough time in art, and it sucks. First, to draw anything from imagination, is your mindset of art. Approaching art with a growth-mindset will definitely help. I used to struggle so much from drawing from imagination. But I changed my mindset and was liberated to explore without fear. 1. You don't have to memorize everything to draw from imagination. What you are drawing doesn't have to be exact, no one will notice the small mistakes unless the big picture is clear. Drawing consistently will help you remember the objects around you, and try not to constantly memorise everything you draw, it's painful. 2. You don't need the exact image in your head, as long as you know the basic proportions and the functions of the thing you're drawing. The minor details you forget, just make it up (that's imagination). If 'you' don't perfectly remember the minor details, 'people' wouldn't know you got it wrong. I recommend watching the Proko videos of Kim Jung Gi, hope this helps. You will get better Anubhav, art takes many years to become "good".