I think the problem with doing a barely visible loose drawing to start with is that its only once its coloured can you see just how wrong some bits were. Loose but not wrong- that's the goal.
Also when it comes to shading you realise how using reference would be a good idea- gets a bit cagey without.
Well you could try to reference on the internet for your silly tentacle homage......... but why spoil it?
Thankfully I'm using these little watercolour blocks- no stretching of paper- so for me that equates to less stress about screwing it up (because it didn't take 2 hrs to wet,tape, stretch and dry the paper only to screw it up- )