I don't disagree with what you are doing, but I disagree with your reason. I am pulling a "Baron Rothschild" today (selling early), but it is not because the company is overvalued (it is not). I have sold about 30% of my position today to lock in gains achieved to date... but will keep at least 50% going forward to the next levels that I think SD will achieve in the coming months.
If you truly believe SD stock is over-priced you shouldn't be in it at all. Doesn't sound financially wise. Based on the q4 numbers and forward guidance (and exposure SD will get in the near future) I believe this company is underpriced - therefore I am adding a little and will add more on any pullback. Of course, trading is different than investing. If your trading time horizon is a few minutes to a few weeks it would be wise not to get too greedy. If you are looking for a longer term investment hold some shares of SD for the next couple years. IMO