In Woolf’s time societal norms, especially amongst the upper classes, were strict enough that many people could not express certain parts of themselves. Not only in terms of sexuality and queerness, but also in terms of the stigma around mental health (and the lack of vocabulary for it) and desires that are outside of societal expectations (such as wanting to marry someone less reputable or not wanting to marry at all, especially for women). Many characters in Mrs Dalloway are exhibiting some form of repression, but most notably Mrs Dalloway herself. Not only is she repressing homosexuality in many readings, she’s also repressing some sort of feelings for Peter Walsh as well as, perhaps, discontent for her own life.
In terms of queerness, it was treated like (as it has for much of history) a secret, something to cover up. Homosexuals were removed from the military, usually with a “blue discharge” (neither honorable or dishonorable), and students were removed from Harvard university. Because of this threat, (as well as the still-prevalant problem of religious pressures), many queer people simply covered up or repressed their identity.
Additionally, and relatedly as homosexuality was classified as a mental illness in the DSM until 1973, mental health issues were also covered up. Often, the “severely” mentally ill were locked up in harsh institutions - in Woolf’s lifetime Nellie Bly revealed inhumane practices - and Woolf herself was institutionalized several times. With this culture of hiding away the mentally ill and the homosexuals, it created a stigma, a shame around both things that would cause people to ignore and repress the feelings. Within Mrs Dalloway Septimus and Rezia are a good example of the shame surrounding mental health as Rezia is often embarrassed by her husband and many times wants his problems to go away for her sake instead of his.
There is a culture of repressing those things that do not perfectly fit the societal mold in the period in which Virginia Woof was writing, and it influences many of her characters, and, very likely, her own life, as she was known to have mental health issues, and also to be a sapphic woman in a marriage with a man.