I agree 100% with reaper, midk and CP. Especially this part:
Captain P said:
And it takes experience, amongst other things, to make the better decisions. Which is often gained by making mistakes - and taking the time to learn from them - , who can only be made when you've done work yourself.
Becoming a good level designer takes a lot of experience, and from what I can tell you're just starting out mapping. My advice would be to keep at it, and to try to improve your ability. The Snarkpit is a great place to get honest, constructive critiques (at least it was and could be again), just be prepared to swallow your pride when people rip your maps to shreds with a critical eye. We've had a lot of mappers come to this site, ask for a critique of their map and leave on a sour note because they felt insulted by the amount of things people found wrong or flawed in their map.
And as a final note, improving your ability isn't an overnight "now I can make uber levels" kinda thing, it's a process, a journey, a pursuit of excellence in design, and it often takes years. I'm not even close to being a great level designer, but I'm able to look back at the stuff I've made in the past, even just a few months ago, and I know I've improved.
Now I just need to stick to a map long enough to show it :wink: