So for example, my sexuality is integral to who I am, far more than my gender: I cannot conceive a version of myself with a different sexuality, whereas in almost all dreams where I am not myself, I am a man. Being disabled is very important to many experiences I have had and I strongly identify with other disabled people fighting discrimination, but I am perceived as and therefore feel more or less disabled in different contexts - it is even conceivable, though very unlikely, that one day I won't be disabled any more. Being white is something I am aware of in many different contexts - probably mostly in terms of consuming fiction, where this one aspect of my identity is treated as not only normal but best (stories have to be about white people!).
Being a cis woman is not an integral part of my identity - I rarely think about being cis at all - but it is a privilege I have and am aware of. Meanwhile, Glosswitch has been wrestling with what it means to be cis:
"To break the stranglehold gender stereotypes have over human experience – distorting and restricting our experience of ourselves – should not involve telling whole swathes of humankind that they “match” their gender. [...] Matching cis maleness – the identity most closely associated with “being human” – must feel like winning the gender lottery. It’s not the same if you inhabit a female body. Who’d want the values associated with that? Yet that is what cis women are told they are stuck with."This isn't how I see it at all.
Being cis gender means I am not transgender. It certainly doesn't mean that I, as a woman, am everything that a woman is supposed to be within my culture - or even any of those things. It doesn't say very much about the clothes I wear, the way I think, my hobbies and interests or my sexuality. This doesn't even attempt to say anything about my genes, genitals or reproductive potential (Most cis women, most of the time, cannot get pregnant. A significant minority of cis women can never get pregnant.)
All my being cis means is that (a) the word woman is the best way I have of describing my gender and (b) this coincides with the way that other people always have described me. Thus cis, on the side of, as opposed to trans, across. This doesn't mean that a trans person and I can't have a very great deal in common - including shared experiences of gender non-conformity and sexuality, psychological dysmorphia issues as well as some crossover between trans and disabled experiences, especially while transgender remains heavily pathologised. But I am not trans and perhaps crucially, I have never received the negative treatment a trans person receives.
It is quite ludicrous to imagine that human beings might be divided between those people who feel comfortable in their assigned gender - along with all the accompanying cultural baggage - and those who belong to another gender altogether (presumably, embracing the accompanying cultural baggage of their true gender). There's perhaps genderqueer in between, and here, the definitions are looser - many cis folk might well identify as genderqueer given greater personal freedom and knowledge of this possibility. However, this still doesn't mean that everyone - or anyone - left in the cis category would match their assigned gender. Gender is a social construct. Human beings use social constructs and are very heavily influenced by social constructs, but we also strain against them, constantly, because they don't bloody fit.
There are obvious parallels with straight folk feeling uncomfortable with the idea of being straight. There are reasons why they might, besides the old "The word for what I am is normal." nonsense (the usual objection to cis, along with "I've never heard that word before so I'm determined to be insulted by it"). A woman may be exclusively attracted to men, but completely reject the norms of heterosexual relationships that her culture presents to her. She may watch romantic movies and not recognise the role assigned to her within relationships; she may reject monogamy or marriage, she may not be attracted to small, quiet, bookish men in a culture that tells her to fancy macho hunks.
But straight is still the most likely way of describing her sexuality. You can still be straight and not fit into a world where the dynamics, depth and even timing of heterosexual relationships is strictly prescribed. You can still be straight and experience discrimination based on your deviance from hetronormative roles, just as almost all cis women, at one time or another, have been made to feel that we are not living up to expectations of womanhood.