Taking things back

So me and my friend always play magic the gathering and I've had a huge problem with memory, (literally it took me a month to remember my friends name) so as always i forget things.
Well we usually play a game of magic and i will try to play something and then realize that something on the field would already have a consequence to this.
In example:
Swinging with a creature while spear of heliod is in play. He lets me take back this mistake but later if he plays a angel and i cast doom blade to kill it, he will try to take it back and argue that its the same as taking back in the later situation.
But when i attacked all that happened was that i forgot about something on the field.
However for him, he now knows i have a doom blade in my hand.
I honestly don't feel thats fair.

P.S while playing he also decides to not inform me of important things like i will go to sack a creature and he will ask which one i want to sack, when there is only one choice like he is banking on me screwing up and takes advantage of the weakness i have instead of the weakness in the deck, he plays to win and always bitches at me when i call him out on being a ass. However this is only when playing magic and he is a really nice guy otherwise.

Take backsies = not magic, if you misplay you misplay and that's how you learn.

Don't play magic like a lamer and let people take stuff back.

"You must, discipline, your mind! And control your emotions"

The more flex you are the more ppl get away with things and take advantage of you.... The game is at its best wen you follow its rules and the rules interact together but the less rules you follow correctly the less interactive the game is

In a casual setting i dont mind if someone goes "pass turn, no wait i havent played a land yet" i am happy to let them put their land down. But if they say "pass turn, no wait i forgot to play a land and then i wanna play this spell ...." that is a no-no for me, even in a casual setting.

As far as declaring attackers and taking it back, if its a multiplayer game and someone just played an anthem or something and didnt really announce it loud enough then i can understand the occasional misplay from the NEXT player attacking into it without realising, but thats about as far as im prepared to bend as everyone really should be paying attention anyway.

While in a casual learn-to-play setting with my wife I take time to let her figure out what's best, and on occasion rewind the game a bit, that's like a magic-class.
Even then, there is no rewinding because of hidden information. If he knew the doom blade was in your hand, because your top card was revealed somehow, then he can argue he forgot. Otherwise, it's hindsight. "Had I known I wouldn't"
If this happens a lot, it may be best for you to learn the hard way. Lose a few games because of things you missed, and you'll learn to double check the field before doing sonething.

The take-back playing creature because you can kill it is just being a total lamer. Forgetting about something like spear of Heliod out is a reasonable take-back, but only one time. The two situations just don't even compare. I'm personally very relaxed with take backs, even in a draft/sealed environment because people can get nervous/anxious and throw cards out without thinking. I like to win because of deck building and strategy. Not capitalizing on simple mistakes because nerves came into play. All things to a limit, course. And that line is pretty obvious, I think. Let's have fun, not get stressed about every move you make.

A guy actually got DQ-Ed while playing against me at states. I ultimated my Liliana of Veil while he had A leyline of sanctity down that he had covered up with his lantern and ensnaring bridge(this was lantern control so it was 25 minutes into game 3) and he called the judge and said I had to sac my own permanents because he was an illegal target and continued to argue this for 10 minutes and appealed it and then complained to the head judge and their ruling was just "he forgot about it rewind it to the closest time the game was correct" therefor after the match they started an investigation and said he was trying to take advantage of game state illegally and dq-Ed him. In other words your friends douchie like this dude when it comes to magic lol