Well to start I think 4 d3 was a bit timid. If your opponent is giving you the center, why not take it with 3 d4? This will prevent those kinds of moves anyway.
Dealing with early aggressive pawns
You really shouldn't post this game as it is still in progress. Perhaps when the game is over you can post it and get further advice. However, I will say that I am in the same boat as you. What I try to do is: before I make any move with a piece, can my opponent immediately threaten it with a pawn, thereby making me immediately having to retreat the piece and lose a tempo. If I know he can immediately threaten my intended move, can I first move a pawn to thwart off his pawn move. I don't know if it makes sense, but it is helpful to me.
Hi Recon777--as a general rule, develop your pieces in layers going from weakest to strongest. There are exceptions of course, like having a bishop on b5 or g5 out in front of your pawns, but you typically want your central pawns out front (e4/d4) with your minor pieces even with them or farther back and everything else walled in behind those. Your opponent violated this rule first with 1...Nc6, which isn't necessarily a mistake since it arranges a quick strike with 2...d5 or 2...e5. 2. d4 would've given you that big center though, and 2. Nf3 was also a more natural response to balance your opponent's pressure on d4/e5. After 2...e6 you could see your opponent's plan of 3...d5 with the follow-up of ...d4 or ...exd4. So again, why not 3. d4 yourself? Then you've occupied that square first and supported your own e5 push, a theme from openings like the French Defense. Even by move four you still had the option for d4, but d3 instead was passive and allowed you to get pushed around. The unfortunate result after 4...d4 was that black had become white, having more space and an extra tempo while sending your pieces backwards already. So in conclusion, be more active and don't be afraid to throw a couple of your pawns out there before the other guy. The worst-case scenario is that you'll lose one or two of them, and against most players that still leaves you with a fighting chance.

I suggest you to play something else in movve 4. If you want to play the KIA, which is a system with d3, you should play d3 and Nbd2 and not Nc3
Recon777: Am I wrong? Is your above-posted game not a current ongoing game of yours? If it is, you are cheating by taking any advice on it. If I am wrong, my deepest apologies

Ok I get what most of you are saying (play d4 before he can) and (don't ask advice related to a current game).
Disregard the game in progress part, I'm not actually seeking specific advice to my current situation. Its just an example of what I'm repeatedly faced with in regards to my friend who is characteristically aggressive with his pawns at the cost of his own position. Its more intimidation and recklessness and if I could use this to my advantage, I want to learn how. I'm not interested in tips about this game in particular. I want to improve my game by understanding what to do when people rush pawns forward, and I want to know HOW to take advantage of the weakness in their position that surely must be a result of that rushing.
Take this (finished) game as an example. Here, I am black and he pulls the same stunt.
And if you're going to say "You're being too timid" you are probably right. I don't typically know how to handle early unexpected material losses.
Here, 3.d5 throws me off balance, not knowing how to manage his threat on my knight. I know you're not supposed to move a piece twice in the early game, so I trusted that he would not take the knight because it'd be bad for him in some way that I wasn't sure about. After that, I sort of lost all focus and ended up playing sloppy, which is what usually happens when my buddy intimidates me with early aggression.
As black, what would you have done after 3.d5? Nd5 loses the knight. So does Ne5. Clearly leaving the knight threatened results in losing it. Moving it results in a messed up position because the only safe spot is B4 which he'd no doubt respond with c3 or a3 forcing me to Na6 which is a pretty bad spot for it. So how is white able to pull off such a disruptive stunt with 3.d5 given the fact that black clearly hasn't played any weak moves up to this point? I'm very curious.
My friend does the same thing when we play a realtime strategy game, rushing a few scouts out to harrass my carefully planned out early base. Its got to be some kind of mentality that I need to learn to overcome or something.

Ahh. Yes that's what I needed to hear, thanks.
You see, I still struggle a lot in anticipating my opponent's possible moves as a deterrant to what would ordinarily be fine moves. So as you say, 2.Nc6 was bad in this case, but in many cases its fine. 3.d5 was entirely unexpected because its unorthodox. One thing about openings in chess I've never caught onto is how the many different openings interact with each other. Its easy to assume that bringing both your knights out in the first 2 moves is never a bad idea. Understanding the practical reasons to vary the plan of the early game is something I really want to learn, but all the video lessons I've seen skip straight from "basic principles" straight to advanced topics. Not really sure where to go for lessons at my level.
Hi all. My first post here, so I hope I'm not out of bounds by asking for some insight.
After decades of only a beginner level of chess knowledge, I'm attempting to get back into the game and understand past the fundamentals. Its hard, because I get rather bored memorizing other people's moves and prefer to understand the meanings behind the tactics. My most difficult part of the game seems to be the transition between opening and middle game. I don't have any of the fancy names of openings (or their moves) memorized, so I just try to play the principles.
Having said that, I have my friend who is also about at my skill level, plus probably 20%. In strategy games, his style is much more aggressive than mine, and he knows it throws me off because I do not have a known defense against the unorthodox. In the games we've played recently, he will advance his pawns to my side, threatening my developed pieces rather than develop his own. I'd really appreciate some insight into a situation like this one:
This is about the moment where I start to get slightly flustered. Obviously, I'll play Ne2 or Nb5 next. There is no sense losing my knight due to his aggression, but either way, my position seems to be weakened, with no apparent consequence for my opponent over extending his pawn. If I move Ne2, I block my white bishop. If I move Nb5, he will no doubt chase me with a6. He loves keeping a constant pressure on, to keep me on the defensive, even if it means destroying his own position structure. I'm trying to figure out if there's a way of taking advantage of this mentality. Neither of us knows any standard openings, so its all just winging it. Is there any advice you all can give me that might help me understand how to deal with someone who does this type of thing? I'm not as much asking for the purpose of the current game - I'm asking so I can better understand this tactic and how to defend against it, and turn it into my own advantage.