This problem is called sibilance and it's a very common problem. Things you can do include backing off from the mic, learning to enunciate "s" sounds with less intensity, playing with EQ to try to reduce the energy in the proper frequency bands, using a de-esser (basically a pre-packaged set of anti-sibilance EQ settings) trying a different mic...
Also, sending it to a mastering house means it's in a stereo mix and so they cannot isolate the one track with the sibilance and correct it, they can only try to minimize it at the cost of altering whatever else is in present in the same part of the frequency spectrum in the stereo file. Depending on what's in the mix, it might be possible without deleterious effect to your production, or it might not.
Much better to reduce it on its own track in the multitrack master.
Check out some articles on recording with mics, use of EQ,
