I think most issues occur because girls have different expectations to boys.
These are massive generalisations for which I apologise but..
- Girls usually like to stay in touch more often, whereas guys would be perfectly happy only talking when you meet up.
- Girls are generally more affectionate and want cuddles and kisses etc, whereas boys use these more to lead to sex than just on their own.
- Girls like to talk about things, whereas guys tend to clam up and hold things in.
- Girls are usually tidier, whereas guys see no problem just leaving rubbish lying around or not bothering to wash dishes or do the laundry.
- Girls struggle to understand how boys can lose 4 hours or more playing a game on a screen.
None of these things are huge problems on their own, but girls can get annoyed by either those things, or things like them, but often we don't like to complain because we know it's not really going to make a huge amount of difference.
I know I sometimes get worked up at my partner for leaving rubbish lying around, because I have to go round picking it up (he just isn't bothered, so leaving it until he did it wouldn't work), but he doesn't see any issue at all with a little mess around the place - so I just get grumpy sometimes as I know there's no point having a go at him.
I am very happy with my partner by the way - the above things aren't about him specifically, and they're only little niggles anyway.