I've been meaning to critique something of yours for a little while now, and I think this picture is the one that speaks to me the most in terms of what's strong and what needs some work.
To start, your line-work is great in this, the varying thickness looks nice and makes both characters seem solid. The pose is also really well done too, I love how their faces are pressed together and the content expressions really make it adorable.
The anatomy of the female is good although her tail seems a bit unnatural in that certain position. I find it really helpful to sketch tails in several different ways and consider which one works best with the pose of the character. As for the male, the only thing that seems a little awkward is the thickness of his front paw, but it's really up to your style preferences if you want to try and define the ankle joint more or just leave it as-is.
I have no problem with the dark shading. The highlight shading seems far too bright, though. It creates an unnecessary distraction from the characters. Lowering the opacity on the yellow glow to about 15% - 25% would make it less obvious and distracting, but still visible.
As for the background, I love what you did with the sky, the colors and clouds look great. The grass has a nice color as well, however maybe adding a couple tufts of grass or a few pebbles into the blank space below the characters may have made them seem more integrated with the scene.
One last thing, the text watermarks on their faces make it hard to see all the wonderful detail you put into their expressions. I understand being worried about theft, but it will definitely be easier to see the art (and still make it hard to steal) if you put the watermark near the neck, ears, or legs of the character. (or you can get creative and stick it in their ear, on their eyebrow, anywhere really)
Overall, I think this is a great piece though! I admire the way your expressions reflect the mood so well, the composition and pose also look really nice.
Hope I could help, and keep up all the great drawings!