David's Sketchbook ;)

[Fedodika]

Wow bro, lots of really really good stuff going on in this latest piece man. You really absorbed those studies well the waves and textures are fantastic, the clouds are gorgeous, and of course I have a few tweaks!

So, the biggest thing, is the sense of scale. In your picture, the boat and the castle look as if they are right next to eachother and the castle and the boat are the same size. Like the castle is a toy or something, only 20 or so feet tall. So what I did was made it smaller, and hit it with a soft brush to add some atmosphere to make it look further. Remember the biggest thing can be indicated as small things on canvas depending on how they're placed. Mountains are everyone's go to thing, so think of the castle as a far away mountain.

I added a bit of color here and there, like saturation, because you seem to be shading with black a lot and while some masters do that for really harsh blacks, they still add rich colors in the shadows. What I mean is when I run the color picker on the sail for example, the tones are very desaturated, and everything around it is very desaturated . So it all gets really close to grey, when sure, there are beautiful paintings that have all the hues really close to grey, but yours could use some more hits of rich color to balance out the painting which is very dark and all the colors are similar in intensity, except the sun or maybe some of the arches in the waves. 

I always use Ruan Jia or the Chinese painters I enjoy, they go way out of their way to have rich shadow colors, so maybe you'll see what I'm talking about

https://www.artstation.com/artwork/d8xvX
https://www.artstation.com/artwork/0ogb8
https://www.artstation.com/artwork/d8b0Q

See how they hit little yellows, purples and shadows that kind of "lift" the values and textures off the canvas

a few more:
https://www.artstation.com/artwork/lxmqo
http://hgjart.deviantart.com/art/Aries-570186455
http://hgjart.deviantart.com/art/Cancer-570318961

It's achived with very light touches and like stripping detail out of things with a texture brush, it adds tons of beauty even if it isn't realistic; it feels realistic.

Also, I think the poses of the characters are confusing in comparison to the scene. The lady seems as if she is casually talking or explaining something and the fellow is calmly steering the boat. Meanwhile the waves are ripping and crashing all around, so it's like the calm sailors in the brutal storm. So one thing you could do to improve that is have their expressions be more panicked, like grasping onto the sides of the boat, or looking very tense. That or make the water less storm like, which i think the former would take less effort.

Great stuff man, also for staying in shape try jogging daily, and doing calisthenics like leg raises, push ups, squats; It's really helped me beat any back/wrist pain since i stuck with it, and it'll pay off long term. don't worry about losing time drawing while working out, you'll end up simplifying and working smarter since you have more fresh blood and neurons running through your brain, it'll only help ;)