Getting discouraged?

Something that happens a fair amount to myself as an artist and musician is discouragement. I think pretty much every person in the human race has had to deal with it at one point or another. The main source of discouragement for me would be looking back at how far I've come with music and having that small question pop into my head which is asking, "have I improved enough?" It's the most annoying thing to look back on how you played your instrument, lets say three years ago compared to the present followed by the ever questioning of whether or not your skill has improved.
This is my struggle and what can keep inspiration from coming to me.
I've found that in order to beat this discouragement you just have to keep on working, keep messing around, and you never know what will come out of just jamming with yourself or fellow musicians.
With that being said, inspiration has struck me and thanks to a bit of jamming around on my keyboard I've started work on a brand new track. How do you deal with being discouraged in the field of work you are in?

Thanks for the comments on my last post as well. I've checked out all your blogs and started following all of you that posted, I must say I'm impressed with the content. I'll leave you all with a video I did with a good friend of mine over a year ago.