In general, I always follow my preshot routine but when I'm ready to shoot I'm with CreeDo:
If I'm ready to shoot and something is bothering me (e.g., my mind talking to myself, someone else moving in my line of vision, my opponent trying to shark me, etc.), I'll just pull off, chalk my cue again (the first step in my preshot routine) and reload.
I don't talk while I'm shooting in order to turn off my speach center in the left side of my brain. And, if someone else is distracting me for whatever reason I'll pull off. If I pull off more than once I'll let my opponent know why and let them know I'll shoot when the distraction is over. Usually they will talk to the distractor for me once they get bored (and that way I don't have to engage someone else -- and, often this sharks my opponent instead).
If it's my opponent that's being rude, sharking, acting like an ass, etc. I'll let them know that I prefer to play geneleman pool but can do down and dirty and then turn into a completely different animal if they (or their friends) want to continue with their antics. At which point I still don't use conventional words after that while I'm shooting. I'll grunt, growl, use pirate lingo like a-r-r-r-g-g-g-h-h-h, lots of body language, etc. And, while my opponent is shooting I'll talk to others (in particular their friends/girlfriend if any) while my opponent is shooting (in a loud enough voice so they can hear me talking about them indirectly while they are shooting; or, even better suck up to their friends/girlfriend and get chummy with them). Might as well have fun using every dirty trick in the book to toy with my opponent if they conciously state that they want to go down that road.
I just have to keep mentally reminding myself that I'm there to have fun, focus on the game and forget about life's distractions. If anything about the game starts giving you lemons it's time to start making lemonaide.
...
Preshot routine is overhyped. The more focus you put into unimportant things that ought to be natural and subconscious (breathing, foot position, practice stroke count, where your eyes want to focus) the less focus you can put on lining up and stroking the shot.
... The point is, excessive thinking about this shít will cause you to utterly shark yourself. It should be as natural as walking, not carefully counted and calculated.
To answer the original poster's question:
Shoot when nothing else is bothering you about the shot. ...
As long as something is nagging at you and you're worried the shot might not work... even if you're not sure why... you don't pull the trigger. You honestly ask yourself what's bothering you, see if you can correct, and if necessary stand up and change your whole shooting plan.
Once nothing at all is preventing you from pulling the trigger, why wouldn't you? Are you trying to bore your opponent? ;D
If I'm ready to shoot and something is bothering me (e.g., my mind talking to myself, someone else moving in my line of vision, my opponent trying to shark me, etc.), I'll just pull off, chalk my cue again (the first step in my preshot routine) and reload.
I don't talk while I'm shooting in order to turn off my speach center in the left side of my brain. And, if someone else is distracting me for whatever reason I'll pull off. If I pull off more than once I'll let my opponent know why and let them know I'll shoot when the distraction is over. Usually they will talk to the distractor for me once they get bored (and that way I don't have to engage someone else -- and, often this sharks my opponent instead).
If it's my opponent that's being rude, sharking, acting like an ass, etc. I'll let them know that I prefer to play geneleman pool but can do down and dirty and then turn into a completely different animal if they (or their friends) want to continue with their antics. At which point I still don't use conventional words after that while I'm shooting. I'll grunt, growl, use pirate lingo like a-r-r-r-g-g-g-h-h-h, lots of body language, etc. And, while my opponent is shooting I'll talk to others (in particular their friends/girlfriend if any) while my opponent is shooting (in a loud enough voice so they can hear me talking about them indirectly while they are shooting; or, even better suck up to their friends/girlfriend and get chummy with them). Might as well have fun using every dirty trick in the book to toy with my opponent if they conciously state that they want to go down that road.
I just have to keep mentally reminding myself that I'm there to have fun, focus on the game and forget about life's distractions. If anything about the game starts giving you lemons it's time to start making lemonaide.