I'm obsessed with photography, inparticular Sports, Scenic & Portrait photography, but time & time again I am not getting the results I am after & am not understanding what to do with what I have.

I have a Canon 40D, Sigma 150-500mm, Canon 50mm 1.8, Canon 17-85mm IS, Canon 430EX II, I take photos that look OK, but I try to crop or sharpen & time & time again I'm just not happy with the results & at the same time I don't know what to do or what I am doing & I'm slowly losing interest & patients with it all.