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Good sex comes down to having a good partner and a decent understanding. It's not magic. If you have someone who isn't willing to do things for you that you enjoy, then you aren't going to have a good time.
I don't just mean will they go down on you or will they ever be willing to have sex with the lights on or last more than two minutes. Obviously that's a part of it. But on the other side good sex is a recognition that it's a two-way street - you listen to and watch the other person and you adjust what you do based on their reactions. There's no great mystery to it, just pay attention. If you're unsure, ask - better the embarrassment of uncertainty than being centrally unsatisfying to someone.
That is all you really need to be decent in the sack. Now when you do that and you see them looking back at you and doing the same, adapting to you, paying attention to what you like, suggesting (verbally or non-verbally) other things that you could like and gauging your reactions to those, that's when you get properly good sex. When you meet people like that and get to properly explore, it's well worth it.
The original question was about the relationship between love and sex though, and I think that's relatively more complicated. As Richard suggested, maybe I'll just go with my take on it.
Everything I said about good sex is almost entirely unconnected to love.
I like casual sex quite a bit. I don't, however, enjoy one-night stands. I think that they are pretty much pointless (unless they're a night that lasts two or three days) in terms of either party getting real satisfaction. But I haven't been in a real relationship in 3 or maybe 4 years. Instead I've had multiple long-term sex partners (6 months to a year), and I've found that to be very satisfying from a physical point of view. I don't think love is part of the equation but you can't help but feel close to someone whose body and mind you're so familiar with - and ideally you can and should if you feel like it. Especially if they've just rocked your world (or you theirs). It can be hard to see past the starts but confusing love and sex was something I did when I was young because I confused a craving for affection with the idea that being loved and being in love are requirements for being a complete person.
I'm not necessarily an aromantic person, by the way. I miss being in love and I look forward to the next time it happens - but as far as sex goes you just need some patience, an attention span, some compassion, a half-decent amount of endurance, and someone who shares those qualities.
There's no doubt that good sex with someone you love deeply is a special experience. For my part, cards on the table, I've had sex with three people I thought I was in love with. With the first, when I was young, the sex blew my mind but I was a pretty terrible partner and it was definitely focused entirely on me. The second time, a little bit older, I put in more, and got more out of it, but sex had lost its novelty and there was always a lack of connection. In retrospect both of us were pretty poor and hit some stumbling blocks. The third was the last time I was in love and it was absolutely earth-shattering because it was a combination of coming into my own (as it were, pun not intended) and meeting someone who was already there.
It was a special experience with all three of them and I don't regret any of my relationships of the three, but the quality of the sex (whether decent, amazing or bad) was never really a direct factor into how close I felt to someone.
It's also worth noting that you should avoid falling into the post-coital trap - all of those amazing chemicals flooding your brain help you bond, but a real connection is more than a rush of chemicals followed by withdrawal.
I am so short on sleep I've rambled on. I hope the gist of it is clear.