Word for something that is not actually hard to do, but doing it goes against your instincts?

Example actions: working out, taking an ice bath, cleaning your house, admitting when you are wrong.

These things are not difficult to actually do, but are often described as hard, when in reality they are things that go against your instincts, so your brain tries to convince you to not do them due to instincts like conservation of energy, ego protection, etc.

The best word I have for this is just “a thing that requires mental discipline”. I am looking for something like non-instinctive, but with an additional clause of not actually being difficult to do. Or when the only barrier to doing a simple task is your own instincts. Does this word exist?

Example usage: “I need to go work out, but I am reluctant to do so because it is really ____.”

Thank you!

I suggest the idiom go against someone's grain:

to not seem right or natural to someone.

It goes against his grain to question the boss's judgment.

[Merriam-Webster]

On a side note, are you sure working out is the sort of thing that goes aainst your instincts? Everyone does "work out" every once in a while if I may say so, right? Apart from that, the suggested idiom seems to cover your question very well.