Right after Sunday's games, I made two bets:
NYG +7.5 -125 vs GB
NE -15 -110 vs SD (I also took NE -14 -110 later that night when the line moved).
Whether these bets win or lose, I know I've already lost because the line has moved where I can easily get a better price right now.
GB is -7 everywhere. That means I can easily get NYG +7.5 -120 by buying a half-point. I was thinking the line would go down to GB -6.5, thus showing NYG +7.5 -125 as a close-to-fair-market wager. So I've definitely lost 5 cents on value, and probably 10 cents depending on how well I shopped for the Giants.
I was surprised the NE line went down. I thought there was a change it would go up to 17. Clearly I'm wrong. So I've alreadly lost a good chunk of EV since the line is now NE -13.5.
These two bets were bad due to line movement. I've had other good bets in the past. I took NYG +7.5 -110 against DAL early last week - the line moved to DAL -7 -110 so I won a little to line movement in that game. I also took NE -11 -110 against JAX, and then bought back JAX at +14.5 -120, so I won on the early bet on NE last week too. That one turned out to be a nice half-middle as NE won by exactly 11 points - not that 11 is a key number, but it is always nice to get a middle or half-middle.
I think keeping records and tracking wins/losses is very important. Without records, it is easy for poker player or a sports bettor to think they are winning when they are in fact losing...or think they are winning more than they actually are. But keeping records for line movement issues takes a lot more work. I wish I had kept more detailed records on that issue the past few years. A good new year's resolution for me is to start carefully detailing line movement issues on bets I make early.