I'm actually going to say that there is zero luck involved in magic, which is audacious... but let me explain.
The other night my wife beat me "on luck." (She plays Gush/Mentor, and I play an Oath/Standstill list with 12 counter spells. Her top decking was insane. Her topdecking was nuts. She drew exactly enough mana to play everything, then threat after threat after threat. After countering a ton of stuff, she landed a Jace and ground me into dust. Woof.... But I really lost on turn two. I played Ancestral on her upkeep, she Missteps, then I crack Black Lotus for blue. I'm sitting on Mana Drain, FoW (with Jace to pitch) and Flusterstorm. I've got the goods... but I get clever. I want her to Force something, so I can Mana Drain it and use the 5 mana to drop Jace on the next turn to win the game... so I get cute and Flusterstorm her Misstep. Boom, she lets the stack clear out and then Flusterstorms my Ancestral and I can't save it. Now I'm in defensive mode. I have to pitch my Jace to my Force next turn to stop Mentor and go on to lose, after she topdecks insanity for seven turns. By the end of that... I'm super pissed, but really its just pissed at myself.
Is there luck? It seems crazy to say no. But what if she just hadn't been playing Flusterstorm? What if she just played a worse deck or something. I mean, she put the card in there to do pretty much exactly what it did. Same goes for all the threats she had. Over time, all these things come up at a predictable rate. And we know that. That's probability... yes, but not luck.
Luck is a completely invented human concept. What if everything in the universe is predictable down to the sub-atomic level, and everything we do that we think of as choice, is already destined to happen...? How much luck is there in MTG then? We don't know... It really comes down to what you want to believe. So I choose two simple things. Namely, don't believe in luck, and don't be a jerk. I'd say your opponent did a terrible job at both of these, and while dealing with that in the short run might be a pain for you, in the long run it will certainly harm your opponent more than anyone else, especially his magic play.
What players are doing when they tell someone else that they got "lucky", is subtextually claiming that the reason that losing and winning happened, isn't just because you made good decisions and they made bad ones (or more specifically, that the sum of your decisions was of winning value, and that the sum of your opponent's decision resulted in losing). That would fall into the being a jerk category. I mean, they've printed over 10,000 unique cards... someone is making the claim that among that variety there was no line of choices that would have lead to victory... among deck selection, card choice, sideboard, mulligan, and then play choices... there was no path to victory because the other guy got lucky...? What an amazing claim! It's really an incredibly narrow view. It makes it sounds like the guy saying it can calc out all the probability of the universe in his head, and figured out that you didn't win on skill... but luck. Yet Leonard Nimoy over here couldn't use this savant-like knowledge to actually find a way to win. An incredible claim indeed.
I'm pretty sure that a lot of players do that because they're emotionally lashing out. Losing hurts emotionally, and since they figure that you hurt them by winning, it's ok to lash out back, and try to stick you with the "you got lucky" tag... But the result of this, and maybe the main reason people behave this way, is that it prevents them having to address the fact that they are actually losing because of real things that they do... or don't do... like not dealing with the fact they're bad at cards.
So if it's all a matter of perception anyway... I suggest you choose not to believe in luck at all. Or rather, choose to believe that a series of choices is out there, that causes you to win. It's there. Try to find it. If it's not there, then pretend it is anyways until you're dead. Then think about what you could have done different. Don't believe that you are subject to luck. Believe instead that you are an awesome magic player... better than the dude on the other side of the table. You can notice details and consider subtle alternatives and find wins. Because your job, ultimately, isn't to tease out the true nature of the universe and luck, its to play cards well. And this belief makes that happen more... and finally, if at all possible, we should all try to not be jerks as much as we can.