/ic/ - Artwork/Critique

Help me guys im at the end of my tether
When i paint from reference i get decent brushwork (at least for what i am aiming at) but when i paint from imagination it looks like a fucking puddle of mud.

It drives me crazy. When there is a reference in front of me i manage to convert it to something that is pleasant to look at, but creating even a flat shape of skin (let alone something that conveys 3d form) from imagination i end up blurring and smudging it into a soulless piece of shit (thats even without getting into my inability to do somewhat decent faces, hence the mask ;_;)

What am i doing wrong when painting from imagination? How do i get my practice of neat brushwork to carry over to when i actually want to render a renaissance oil-like masterpiece of my big titty animu gf?

Any and all suggestions appreciated