There is so little in Aikido that makes you feel like you are doing well or getting better. When you lose faith in yourself and try to step out of your comfort zone, maybe by sparring with someone who practices something more sparring-oriented, or exposing yourself to a different system, you generally don't find that you were wrong about sucking.
My belief is that spending too much time in a sparring or sport system really gives you false confidence that the ring equates to a live fight, but false confidence is still a kind of confidence.
I like the first part of your post. The basic feeling in aikido si more or less: If a technique feels good, you need to work on your awereness. I like it, thereīs always something that needs polishing.
About the second part: The sportfighters Iīve met have been much more humble about the difference between their practice and a real fight than many aikido-practitioners that Iīve met.
I think itīs very natural that most aikidoka are unsecure about their abilities, how confident would you be in your swiming abilities in open water if your only experience were practicing the movements on dry land or in a very shallow pool?