Well my opinion is, mastering the guitar has nothing to do with speed.
Look at Andres Segovia. To many, including myself, he was and his a guitar master. He never focused on how quick he could or should play, only how well he could sing each notes with his guitar.

Speed players tend to be messy. Sure they are really impressive (technically) and I'm trying to improve my speed too but we have to remember that music is art. Its not about how fast you can paint a nice portrait. It's how your gone be able to translate the person's emotion into your portrait. There is place for speed but it shouldn't be our main concern.

Ok so that was my opinion on speed. Now to the subject. For a while I have been working on my improvisation. Every time I reach a new step, I say to myself : " Ahh ! now I'm getting good ". Then I look up and see all the other stairs that I have to climb before reaching the level I want (but we all know that once I get at that level, there's gone be other stairs right ? :)) I say this often on the forum but the best thing to do at that point is not to get discourage. To stop looking up and enjoy our music on that step. Sometimes looking down and seeing all the progress we have made can help with this.
Have fun and remember that there is no limits in life, only the ones you put yourself.