People, sports teams and armies usually tend to "play" up to the strength of their opponents. This can also be the same as playing down to a level for some top players if they get sucked into foolish play. I actually found now that im getting better and playing tougher opponents mixing it up can catch them off guard. With a game plan in mind of knowing what they want to do and acting in a counter . Sometimes delaying castling to a side that is convenient right "now" but maybe isn't best location for a king long term has helped me lately. I think as we get better in chess we stop just looking at what we want to do but rather thinking of what an opponent wants to do against me thats more important. Without a plan in chess your playing with fire which low level players tend to do alot. Everyone learns from better players.
Playing lower ranked players

Your not alone, sometimes my opponents make positional mistakes that just throw me off, I start getting confused thinking "I should have to fight for the advantages you are giving me" and it often distracts me and I play less careful and sometimes mess up.

I have no problem beating lower rated players. I lost only by experimenting on openings, making speculative sacrifices. Playing my normal game makes it too easy and boring.

I think the hardest part of low ranked players is when some of them play a normal main line for the first several moves deep.
Than all of a sudden they deviate into some obscure variation.
Usually it happens when they ran out of theory and don't have a clue what to do.
Other times it is when they have a unique pet line which they have studyed deeply.
An you are left thinking to yourself.
How do I punish these morons lol.
Than ultimately get frustrated when you can't find a clear refutation.
At which point you get upset and leave the chess game completely angry and frustrated.
I have gotten beat by a low level player in the below chess line.
The move e5 allows black to equalize.
Black is said to be doing completely fine here.
In the game, I knew I was fine here.
However, I still managed to lose as black lol.
After a few odd looking moves I sometimes start to lose focus. Not blunders, more like a few ?! moves.
Other times I enjoy it and seem to work extra hard to make use of the mistakes.
Lower rated players are definitely harder to give you best game though.
I lose a surprisingly number of games to (much) lower rated players in blitz who have no idea what a 'standard' opening line is, and who proceed to blitz me with a whole slew of inferior moves that I don't have the time to refute in a blitz game. Stuff like crazy kside pawn rushes, unsounds mating attacks, and unsound sacs on f7.
Against players my rating, it's usually the case that the first 5-10 opening moves can be played mindlessly by either side as we typically know the book moves or at least 'solid' moves up to there. We then get a bit too comfortable having the first 10 moves pre-played for us, and lower rated players get surprised us in blitz by making us burn time or misjudging our position early on.
The most realiable way to beat lower rated players I've found is to draw out the game as long as possible. Safe, small developing moves with intent of playing into an endgame (but not liquidating into an endgame too quickly.) The more chances you give them to make mistakes, the more mistakes they will make. Unfortuantely, this does mean you have to give up your ideas of winning the game in 25 moves or less - I tend to overpress when I try and 'blow away' these weaker players and end up giving them too much counterplay.

@logozar
Very good point.
Yeah I haven't ever tryed that variation before.
Maybe I will give it a try next time I face 3.e5.
It is not the greatest move.
However, you be surpised how some low level players can play it very well with a lot of home preparation.
Am I alone here or does anyone find that you play better against higher ranked players who are more polished and sort of "do what they're supposed to"? I've played some lower guys who get all crazy and my over-confidence kills me as their beginner kamakaze strategy actually works. You gotta slow down with these guys and just bat their dumb strategy off like a fly.