If you're not factoring opponents making terrible, donkish plays in your decision making whilst playing micro stakes & freeroll MTT's and taking careful & intelligent precautions against that, it's going to end in tears.
If you want to argue that getting sucked out on by maniacs or clueless muppets is evidence of a big online poker con then I'd like to direct you towards the rigged mega-thread. [emoji1303]
I had an interesting hand the other day.. Dealt pocket 88's in position I raised pre and we go two-handed to the 822 flop. I bet the flop hoping he'll think I'm just continuing/stealing. He calls. Great. Turn shows 822,2.. Well, it's unlikely he has a deuce and even if he has AA he's pretty much dead to two outs. Although I'm almost always miles ahead I now want to shut it down or get maximum value so shove all in. When he calls I'm momentarily worried, when he tables AJh, I'm relieved. He can't hit an ace or jack to beat me and has maybe 1.9%
equity. The river (of course) comes the case deuce and he wins with a higher kicker behind our shared quad deuces.
Now, some might argue this is evidence for something or other, it's too much of a coincidence or would never happen in 'real' live poker. It isn't, and it does.
Even though someone has just one out on the river, that one card has exactly the same chance of hitting as any single other of the 44 remaining cards.
Is it unfortunate to lose a big pot in a tournament? Sometimes. Am I upset by it happening? Perhaps for a second. Then it should dawn on you that you got your chips in a 98.1% (or whatever) favourite and pretty much as close to always as possible in poker, you're the one counting that pot into your stack.
If you can't see the positives hidden just a layer or two underneath these situations then in my opinion you're in need of a perception shift.
As someone else already said, I don't know what to tell you...
If you can't take emotion out of the equation and embrace variance then you might want to figure out how you're going to move forward because losing big pots or someone catching a miracle card are things that are always going to happen at some stage. It's inevitable.
Work out how to navigate around, or insulate yourself from, this.