I've been playing bass for several years and I'm still learning something new everyday. For a while I've realized that as bassists we have a very important role in a band. A good bassist needs to keep time, keep rhythm, keep groove, keep melody etc. A good bassist is aware of what the drummer, guitarist, vocalist etc are all doing apart from focusing on his/her own playing. Which means that a good bassist is the glue. When I started I was very flashy by virtue of having been a lead guitarist for sometime. Then I realized that while flashy is cool...fulfilling the above role is much cooler. Be flashy once in a while but remember thy role in the band. This is easier said than done.
The point I am trying to make is that if we have to improve in our role, we have to go beyond what we know. Jam with better musicians. Not just other bassists. Great drummers will get your timing in shape. Great guitarists will get your sense of groove and rhythm in place and great vocalists are excellent sources of solid melodies. Everytime you start thinking "hey I am really awesome at this" go and find a more experienced/knowledgeable musician and jam with them. It will be a beautiful reality check and you will always be at the top of your game.
This is of course not just useful information for the bassist. This is equally important for every musician. Want to become better? Find better. And when you do, jam with them and later talk to them and be very open and ask them "hey is there anything I could have done better?". NEVER fall into the trap of thinking that you are super awesome just because you think you are better than those around you. Make the effort and go find better than yourself.
WOKAY. Enough lecture. Go Play.