To value bet or to bluff? That is the question

I have made two large post it notes, one says 'value bet' and one says 'bluff.' All bets in poker are one or the other and I have had some problems automatically betting without a good reason either way. My polarised post it notes are helping me to keep a check on my reasoning. I should also be able to isolate problem situations where it is not clear cut either way. For those who are not clear on the definitions a value bet is a bet which stands to be called by a range of worse hands eg you bet AK on a KJ8 board into a passive player who will chase draws and peel with middle or bottom pair eg JQ, J10, J9, A8 etc. Some of these hands will be superior hands, such as 88 but it is still a value bet when you make it, since there are fewer monster hands that are potentially ahead of you. A bluff is a bet that will fold out a range of better hands such as a donk lead on a A72 board with 64. Your hand is worthless and you do not want to go to the river only to be beaten by 9 high, so you bluff and your opponent will likely fold KQ,KJ,QJ,J10 etc to a bet thinking that you hold an ace in your hand. To make these bets you need to know your opponent's playing style and mood, since a tight aggressive player will pay off obvious value bets less often than a calling station and a tight-passive player will often fold to bluffs.  The psychology of betting in poker fascinates me and I think the reason why calling stations call with such a wide range of hands is that they fear being bullied and they are also eternally hopeful about the hands they might make if they get lucky 'this time'. This is why you should rarely bluff at nanostakes poker, because you are playing against people gambling for fun with very little money. They are happy to splash about their chips and so you should value bet the living daylights out of them every chance you get.