This is a pretty well articulated post and something I would imagine so many players struggle with on some level.Getting Run Over EarlyWith just a single opponent, fairly aggressive and unknown players often playing each other and a great deal of variance, you're bound to get into some matches where you just miss boards that your opponent can likely hit (and does) and you face a great deal of legitimate aggression.The key is to separate what is "likely legitimate aggression (IE: top pair check raise, strong draw check raise, 2nd pair flop lead, strong hand 3bet)" from what is probably a bluff.The obvious signs that you're just being ran over by bs type hands are the types of boards you're being played hard at.  Genreally speaking, weaker players are going to bluff you too often on dry boards, stronger players vary and may be the opposite (bluffing you much more often on wet boards that more likely hit their hand ranges and make sense for more hand combinations to raise you).Another thing to take a look at: Have you seen them show any signs of passive play?  Have you seen them get to showdown yet? With or without aggression?  If you see a guy checking down 2nd and 3rd pairs, Ace and King high but playing super aggressively otherwise, odds are he's bluffing you quite a bit and overplaying a tremendous amount of draws.  But unless you adjust, he's not technically bluffing you too much nor overplaying those weaker draws at all, since you're folding too often.New Aggression With A LeadThis one is tougher to answer without a very specific situation (best exemplified by being in the moment live or watching a situation of this happening in real time).The best thing you can do later on in the game, with a lead, is to keep playing based on the reads you've developed.  Unless you're playing a very strong player, it is unlikely that your opponent can figure out what image he has given you and how to manipulate it to his advantage.  More often than not, if a player has played tight and wants to play back and rely on that image, he'll just show a ton of aggression.  But a majority of the time (except for very good players) your opponent will still give off too many tells/tips that he doesn't really have a hand.An example would be a fairly tight player raising his button.  You've seen him value bet you earlier with an overpair, perhaps KK on a board with all under cards.  He half pots the flop, turn then under bets the river for value.  You call down with 2nd pair and see his overpair and he takes down the pot.However, he hasn't connected too often since and you've taken a chip lead by being aggressive, betting when he checks back flops with scary cards and often has nothing, check raising dry boards he seems to fire at too often with bluffs (and isn't playing back at you yet) and so on.So he raises his button, you call, and he pots the flop.  You have 2nd or 3rd pair and flat call.  He then pots the turn.  You call again.  He then shoves the river for an overbet.  You call.  He flips over air then berates you in the chat asking you how you called down so light when he was repping the nuts.  Sound familiar? Board texture and specific reads obviously matter, but these situations happen over and over.  You know the player isn't likely to have as strong of a hand as he claims, since he value bet his overpair so weakly earlier in the match.That is a simplified version of how to catch players misapplying "image" adjustments when down, but that should be a good start.General Momentum ThoughtsMomentum is something I think about, particularly when rematching somebody over and over.Certain players will play very well when running good, but when things go bad for them they really lose their footing and start to spew quite heavily.  Therefore, the ideal adjustment is often to quit somebody who is both running and playing well, and to keep playing them when they are spewing/tilting.  It makes sense because you may not have a big edge (or any edge at all) when they are at the top of their game, so if you get off to a bad start in a session against a particular player, feel free to quit them.  While you can always start to run well at any time, many opponents don't seem to remember or take into consideration previous results from previous dates, so if they took 5 buyins off you on Monday, Wednesday night's -2 buyin start for them could very well set them off.  At the same time, if they take 5 buyins off you on Monday and you keep playing, a 2 buyin swing may have little to no impact on their play.There will always be a ton of variables to consider.  Some players may play bad enough when winning to where you should keep playing them (as long as you are playing well).As far as momentum within a game goes, if you're playing a longer structure (say Stars regular speed, but really anything other than FTP turbo and super turbo) you can often see some momentum within the game if your opponent (or you) are running good.  The best thing to do is just to think about the things in the first two sections of this post and to keep your confidence up.  The better you understand that bad variance is normal and will happen, the better you will be at holding your own in the worst of times, which will have a great impact on your edge and ultimately profit. 

It feels like you could be striving for too much "black and white" answers to these problems, though you're on the right track.Against the guy that bluffs like crazy, why make a large raise with middle pair if you haven't seen how he responds to aggression and you still have some large stack sizes?  If he's firing bets all over the place, keeping his bluffs in his range sounds like a good idea there (specific hands and boards can always change things of course).As for the player that fires a lot and you just don't have a hand, fighting back is a good idea.  Generally speaking, the most loose and aggressive players will play much more loose on earlier streets, so bluffing them in turn and even river spots with air can be the best adjustment there.  Why?  Well they will call off with any draw, any pair, any high card and even air (to steal the pot with later) on the flop, since they have two cards to come to play around with or make their hand still.  On the turn, you see less of it, but still more loose play than on the river.  Then, unless you're really a very aggressive adjusting player (which is great if you can pick out really good spots to fight back on earlier streets, but that's going to be much more difficult in general), they will be at the river with a very wide range of hands, a very weak hand range and they will be in a fairly decent sized pot more often than not.  This is a particularly great place to attack the loose aggressive player, as no more cards will come out and the pot is large enough to where 1) It's super valuable and 2) They can't just call with K hi to a huge bet or raise any longer.

That can make sense, of course it is situational.But remember, like calling a shove preflop, you just want to be ahead of their range, not feel like "you can't be beat."  So if the opponent uses the higher cards to bluff (K83 flop you have 87, turn T, river A) then you will still be beat sometimes but he'll be bluffing much more often.