What is it?
I have a habit of always using Mieses. Should I work on using some different ones?

Oh, 1. d3. It's not so bad, but also it's very bad. You can follow it up with Nf3, g3, Bg2, King's Indian Attack style. There are better, more flexible move orders to reach KIA though. Generally speaking, d3 is very passive and unambitious.
The idea of playing d3 to defend against a queen or bishop move is wrong. d3 doesn't protect against this and you basically never want your king on d2 anyway. Also there is no reason to protect against this as it's usually not a threat if you play e4 or d4. Even when it is, it can be defended and you will have a much better position than if you played d3.

"opposition attacks with bishop and queen (where?) so i give my king a space (on d2??)"
your main statement on why you use 1. d3 is confusing and flawed

It started as a defense for when opponents would come in with a bishop and queen. I needed a space for my king to escape to.
I don't understand what this means, and I'm afraid to ask. Playing d3 in order to later play Kd2 just leaves me without words.

i think i understand the op now and i am so baffled
apparently, d3 is a defense to e5 Bc5 Qh4 Qxf2 so you can go Kd2 after all that
so you are just passing three moves?
Nf3 defends h4, g3 e3 h4 AND d4 all block Nh3 defends e4 Nc3-e2-g3 blocks you can literally castle by the time they are finished with their attack (e.g. e3 Bd3 Ne2 0-0, most reasonable ways to do this defend by itself)
this is even worse than anyone thought, if true
please do stop this immediately
edit: so does e4 Qe2, e4 Qf3, d3 Bf4-g3, f3 Nh3-f2 and h4 Rh3-g3, d3 Be3
not saying all these are good, just... assuming you will pass thrice in a row is stupid

I didn't know all this. I'm new, never had lessons, just learned a little bit of chess by farting about with inbuilt games on my computer.

understandable
though is it a good strategy in a war for the leader to run in front of the enemy forces, which can demolish him and then the army loses faith
and besides, just blocking the attack is better

I didn't know lol. I'm pretty new, only played a few months. I barely know my butt from my elbow on a chessboard.

I LOVE the mieses!!!! I TRIED playing the maroczy/fantsy to unite my caro theory with my alapin french & BDG theory, but black kept declining it, so i started playing Be3 and THEN black takes on d and usually f3 to get my knight developed and then I have a knight, a bishop and a pawn developed vs. black's pawn.
this is just playing with one or two book study sessions and otherwise playing by instinct. THIS opening agrees with me. I've won my last 6 in a row in fact and especially do well when the gambit's accepted. OH! I think I created an ...Nf6 declined book and studied that too, now that i think of it because declined gambits suck and i needed improvements. My record is 0 and 3 in that
THIS is why I love the mieses
very much king's gambit tactics using the open f file with space to get my pieces out

I tried using d4 rather than d3 and went on a big ol losing streak.
I was tilting for other reasons, but it didn't help that I didn't really know what I was doing.
Went back to Mieses and won a bunch of rating points back, but I would probably have done that anyway, I just got gold membership and started doing a bunch of puzzles daily.
Might need some help from a coach to detangle this.

I thought it was a line in the scotch, anyway, 1.d3 isn’t great, but not that bad, I would probably play a KIA if you choose this as your first move 🐸
It started as a defense for when opponents would come in with a bishop and queen. I needed a space for my king to escape to.
Should I work on learning other openings instead of sticking to just one?