The whole idea of lowering one’s standards sort of misses the point. Being in a relationship or not, if one isn’t satisfied with it, it will just make both people in the relationship miserable. That said, sometimes people have unreasonable standards, not in the sense that they’re particularly unatainable, which they may or may not be, but because they THINK they need something to be happy when they really don’t. If you take the time and really think about what you NEED, and relax on the things you really don’t, you’ll end up a lot better off.
For instance, there’s the obvious “she has to be hot”. Aiming for some generic level of hotness, like an 8, really isn’t going to do much good. From my own experiences, I can easily say I’ve seen some girls who are clear 9s or higher, but don’t really seem to do much for me, where another who would generally be rated lower, maybe a 7 on most people’s scales, seems to pique my interest more. As such, my only real criterion in that regard is “attractive”. Of course, this probably is less necessary for meeting someone in person, since you know whether she does whatever for you, but it’s definitely worth noting when it comes to online dating. When I was doing that, plenty of times I’d see pictures where they looked fantastic, and for whatever reason just wasn’t really attracted to her, and others where I felt like she might be marginal, but was really attracted to her in person.
Or for other less superficial things, I’m well educated and it’s important to me to be with someone I can have a good intellectual discussion with. More than a few times I’ve dated women with advanced degrees, but can really only talk intelligently on that narrow topic, and others with less formal education, but have a genuine curiousity and can talk intelligently on all sorts of things. And, at that point, and why I changed a standard from “well educated” to “intellectually stimulating”. Similarly, I’m a musician, but can ultimately really connect with just about anyone who is passionate about some form of art.
And, just as important and often underlooked, it’s just as important to make sure some aren’t too low. Someone might be willing to accept someone who is significantly less intelligent, artistic, active, generous, or whatever other things are important to them because they don’t realize how important those really are to them or, perhaps worse, don’t feel they deserve someone who is that.
So, really, it’s not about lowering one’s standards as much as really assessing and defining what one’s standards should be. Sometimes they’re too high, sometimes they’re too low, sometimes they’re just plain completely off the mark.
And for the “practicing” in the OP, I’d generally not suggest that unless both people are on the same page. The thing is, I’ve known a few people who have done that, and would even refer to them as “practice girlfriends/boyfriends”. In every case, they really weren’t very invested in the relationship, where the other person was. And, if they did learn anything, it really ended up being bad lessons because they learned to manipulate that difference. Like knowing she’s more invested and he doesn’t really care, he might go out and do something for himself where he should be spending time with her. In one case, I know a guy who managed to convince his “practice girlfriend” that he needed to sleep around but she didn’t, so it was going to have sex with other women and she would just let him do that, and by the time she realized she was being manipulated, she was crushed.
Really, what sort of “training” is required? Sure, there’s some basics like, don’t be a jerk, don’t be a slob, treat her like a human being, but if you actually care about her, that’s the sort of stuff you’ll be inspired by that not to do, or see that it makes her unhappy and make a simple effort to fix it. Similarly, if there’s things that bother you and you care, you’ll have more patience and be willing to work with those flaws. And if whatever they are are insurmountable, maybe you’re just incompatible and you move on.