Like everything else, "tech", it's just a matter of practice and confidence.
I'm now very much a "late adopter" of all modern tech. When I was young I embraced it all, I bought one of the first computers, a ZX80 back in 1980. I had a mobile phone in the early 90's. But, as I've got older, I'm more reticent. I now let others be the "early adopters" as they're better placed to be the guinea pigs whilst new "tech" becomes established and the kinks/errors ironed out. I've only just got into music downloads, bluetooth, etc.
But at the end of the day, the more you do something, the more competent you become at doing it. Learning how to do something inevitably means making mistakes, spending more time learning, etc. So the key is to try to learn new things when you have the time, aren't stressed, etc. Not a good idea to try a self service till the first time when you have loads of shopping, the shop's busy and you've only got 5 minutes left of your lunch hour. Far better to "trial" it when you only have a couple of items, the shop's quiet and you've got time.
Trouble is that some people won't engage with new tech until they have to. Rather than trialling it at a convenient time, they just deny it's existence, therefore they don't learn how to use it, and are then caught out when they find that there are no alternatives or that they have to use it at the worst possible time (i.e. busy shop, full trolley, no time, etc).
Tech is here to stay. If you don't want to embrace it, that's fine, but you'll be the one to suffer in the long run. Makes sense not to go rushing into anything new (early adopters usually struggle), but to dip your toe in the water when things become more the "norm", learn how to use it, and then you're ready for when there's no choice.