Opposite idiom for going with the flow

According to the Cambridge dictionary, going with the flow is defined as to do what other ​people are doing or to ​agree with other ​people because it is the ​easiest thing to do.
I am writing a paper and I'm really stumped as to what would be an idiom, or a way to describe a person who is not going with the flow.

Specifically, the sentence which I need this for is this:
I have had to come to terms with a lot of cultural differences which has been a struggle for my ____________ personality.

Note: I am specifically asking about an idiom, and not words such as: inflexible, rigid, stiff, unadaptable, firm.

Solution 1:

If you don't go with the flow then you go your own way or do your own thing. Admittedly, for your sample sentence, go-my-own-way personality might be a bit cumbersome. So you may prefer independent or independent-minded:

[independent-minded in Collins Dictionaries:] self-reliant and seeking autonomy

-minded in Cambridge Dictionaries:

having a ​particular ​character, ​interest, or way of ​thinking about things:

She's very ​[] independent-minded (= she has a very ​[] independent ​character).

So, to see how it sounds in your sample sentence:

I have had to come to terms with a lot of cultural differences which has been a struggle for my independent personality.

I have had to come to terms with a lot of cultural differences which has been a struggle for my independent-minded personality.

Solution 2:

How about "going against the grain"?

https://en.wiktionary.org/wiki/against_the_grain