Yes -- I keep lowering mine. My original goal was 150, then 147, then 145. Now it's 138.
Honestly, I don't even know if it's achievable and realistic. I've never been below 147 lbs. in my adult life. I'm trying to be ambitious here, but it may be too low of a weight for me to maintain. Gonna see how it goes.
I have to say, I think you are smart in being realistic! And a goal is just a goal, an idea. No reason you can't change it. I may very well change mine back to 145.