If you're learning perspective, thousands of quick sketches would serve you much better than spending three hours on a pixel-art piece, hahah. If the base drawing is bad, no amount of pixeling is going to fix it.
If you're a lonely artist like me, who hates practicing alone, check out a paintchatting community, like niko's paintchat, or mangamasters. Lots of fun, and if you're like me, you'll learn faster that way than drawing alone. Having a bunch of people watching in the room keeps me honest, hahah.