No mishaps yet here, but I tried to avoid all the potential mishaps I foresaw myself making..... many of which were listed here

One thing I did was
buy these
Amber storage bottles size 120.mL, amber glass, PTFE/silicone septum, O.D. × H 49.mm × 114.mm, pkg of 12.ea, thread 22-400 | Sigma-Aldrich for use with a syringe and sharp needle.
The second I did was get these
Dispensing Syringe Tip Cap Pack of 100: Syring Caps: Amazon.com: Industrial & Scientific and dedicate syringes to specific liquids. IDK if it's right or wrong, but I generally don't clean the syringes with these, their air tight and as the syringes were sterile before I used them, and nothing but "that" liquid has ever been in it, and is trapped in it when closed. Figure it's the same as PG/VG in a bottle. Would love to hear any thoughts on that though, just cuz it make
sense to me, don't mean its right
I do this with my flavorings. The 3 mL syringes I bought have little caps, so rather than hassle with washing those, I just keep the cap on the syringe when I'm done with it. I wash my blunt tips in vodka. I hate having to wash/rinse/get up from the table in between adding flavors especially since I have gone somewhat psychotic in how many I've been mixing lately

I made 16 bottles this weekend, though only 10 of those were new flavors to try..6 bottles were for friends.
I have found that when I am doing something with the potential to be dangerous if I make a mistake (passing meds to patients, hanging multiple IVs, stuff like that) I must come up with a step by step procedure and then ALWAYS do it that way. When I get "creative" and change up my method is when I make mistakes. When I get distracted, I make mistakes.
So I've kind of come up with a system like that for mixing too. Perfect example though..I have my recipes written out a certain way. Last weekend when mixing, I had one that was kind of long and it was at the bottom of the page I was writing on, so I wrote one of the flavors off to the side. Sure enough, I forgot to add it and had to dig that syringe and flavoring back out. The good thing though, I KNEW I had forgotten to add it because it didn't get crossed off..one aspect of my system. Minor setback for sure, but it also keeps me from doing something fun like adding nicotine twice or somesuch.
I really like this thread..I hope we keep it alive because I am all about learning from other's mishaps and methods. Tell me more!