It depends not only on prior experience but also, which brand is being used, when it comes to meds in general - not just benzodiazepines! My first ever experience with diazepam was me taking 100mgs and feeling absolutely zero, so nothing at all, no sleepiness, nor any kinda relaxation to speak of - and me being on top of that completely sober beforehand and, subjectively, afterwards, too! When I later got the liquid preparation of it prescribed, it's a totally different encounter and the stuff working properly at appropriate, low doses (with no tolerance). I then have had other compounds of this class and all of 'em did their job, with the sole exception being their potency (=overall effects) which was every time differently in relation to what brand I had of the substance I ingested, so once again "Tavor" that's sold by Pfizer was active at 1-2mgs, while a cheap generic wasn't nearly that good (potent) at all... Benzos are, to add that to the general consensus, most likely but not exclusively, prone to make ppl think they're stone-cold-sober and fine, when they're obviously not, as many of their effects are rather subtle and depending on how they're felt, what their purpose of prescribing them, is - logically, I'd say! This is unfortunately a problem if taken recreationally, for what they're just not intended as they're often not suited to make one feel as 'high' as when compared to other compounds, which then might be a good way to get one into trouble/situations that are possibly not planned...
Potency of a Substance has, in my experience, nothing to do on how strong you may think you'll "feel" effects in question, which is most pronounced as to what's the main property of the benzo - so Xanax didn't do a thing for me, as it's not much likely to add to ones (muscle) relaxation, but diazepam was okay and Lorazepam was the best, subjectively felt, at least (but Xanax, Alprazolam, and Tavor, Lorazepam, having the exact same overall, rather high potency).