There is a lot of information on here about pre-shot routines, but not so many on post-shot routines.
You need a post-shot routine just as much as a pre-shot routine. It takes place after the cues follow through comes to an end. It can be something like counting to 3, then getting up, walking over to the next shot then starting your pre-shot routine. All post-shot routines must involve either watching the CB or OB. I'd advise watching the OB. I've got a buddy who when he misses always asks me did I miss thick or thin? I'll tell him, but if he watched he could see he missed his intended part of the pocket by 4 inches, so next time that shot comes up he can make the necessary adjustments. But there are lots of current and former world class players that watch the CB, so it comes down to preference.
Remember, pre-shot routine - shot - post-shot routine.
Slowing down your play may not be needed unless you don't give yourself time to think about what you're about to do. Ronnie O'Sullivan thinks at least 5 shots ahead all the time. My snooker and pool brain can't work that quick if I was to play at his speed, but others may be able to. General rule of thumb says 3 shots ahead for rotation games, so really think about those 3 shots before you even take on shot 1. If you do think 3 shots ahead in rotation but but rush the shot, so your intended plan doesn't work just stop and recalculate the next 3 shots. This shouldn't happen in theory but it does. You shouldn't be rushing a shot. Always use the same number of practice strokes, for me this is 3 and I pull the trigger on the 4th stroke no matter what is going on around me. I've seen players use no practice strokes all the time and some that use 13, what ever suits you. You use practice strokes for just that...practice for when you pull the trigger. Don't practice stroke at 100mph and then tap the CB. Pull back slowly, and accelerate as you will when pulling the trigger. It massively improves speed control this way as well as slowing you down. Try to incorporate a pause in your stroke also. I have 2 pause phases, one at the CB and the other at the end of my backswing. They're not 10 second pauses so it won't slow you down much, but it really helps with the timing of your stroke and keeping things consistent. One final thing I do that slows me down is to chalk at the end of my post-shot routine and again during my pre-shot routine once I've positioned my self to view the shot before stepping in and getting down. My chalking time is my thinking time and this can really help with slowing you down even when you are anxious or nervous or excited.