Len, I would sell if I felt iffy on a stock and I had a nice one month profit. But lets talk about MDF for a second, everyone else will give you the bullish case (seems to be the consensus on the board on this one), but I'm clearly not excited when I see this stock and I'll tell you why.
1) Stock is not cheap, by any means, and costs could be up significantly because of expansion plans which may take some time to get off the ground, so might not be accretive in the beginning. Futhermore they didn't pay taxes last year, so if you net earnings of taxes (eventhough they didn't pay taxes and actually recorded a tax benefit) you are probably paying about 20 times earnings if they were taxed.
2) Company is obviously dependant on Humana, yet I don't see that relationship being severed anytime soon, but still adds some risk to the stock nevertheless.
3) Stock isn't that far from the highs.
4) Think first quarter results, might not be that great, but could be wrong, but have to be for share price not to go down.
--Conclusion: Obviously this is all just my opinion, but if I felt like you with your doom & gloom attitude towards the market, and I had a nice 38% profit in one month, I would take it and move on, especially if you feel quesy, sometimes your gut is telling you something, sometimes it doesn't, but generally I follow my instincts, but it depends on the type of person you are. And since you broke your rules to buy the stock, maybe you should break your rules and sell the stock. However, the question you have to ask yourself, does it bother you more to see a stock go up, after you sell it when you made a decent profit or hold on to a stock that you had a decent profit in, and watch it evaporate in front of your eyes, and maybe even lose principal as well. The answer to that question for me by the way is I rather hold onto my profits, and sometimes I leave money on the table, but thats me, it really depends on your personality makeup. Once again I reinforce that this is just my humble opinion, and I have been wrong before, and will be wrong many times more in the future as well--