There are of course many examples of this governing theme in this novel, most of them situated around the way that Elinor and Marianne react differently to the problems in love they encounter. Mostly, however, these reactions feature a much larger debate, which concerns how women should act and whether or not they should follow the dictates of society. Mariane is a classic example of a young woman who wants to try and break free of societal restrictions and ideas of what a woman can and can't do, and this can be clearly related to sensibility. Note how she responds to Elinor--the voice of sense--after Elinor tells her she has been too expressive with John Willoughby:
Elinor," cried Marianne, "is this fair? is this just? are my ideas so scanty? But I see what you mean. I have been too much at my ease, too happy, too frank. I have erred against every common-place notion of decorum! I have been open and sincere where I ought to have been reserved, spiritless, dull, and deceitful. Had I talked only of the weather and the roads, and had I spoken only once in ten minutes, this reproach would have been spared.
The reader can clearly understand Marianne's frustration of being trapped in a time where women are meant to be "reserved, spiritless, dull and deceitful," but at the same time the way in which Marianne reacts later on in the novel to Willoughby's desertion of her, compared to how Elinor reacts when she finds out about Lucy's engagement with Edward, exemplifies the dangers of sensibility. The novel ends with Elinor having a new appreciation of her sister's sense, and having learnt the importance of balancing sensibility with sense.
In Austen's 'Sense and Sensibility', the title itself is given the significance of being a major theme. Austen portrays two characters, Elinor Dashwood and Marianne Dashwood representing the theme, 'Sense vs Sensibility'. It is important to know that her one intention of writing this piece of literature is to parody the conventional form of novels which were highly romantic- and therefore celebrated 'sensibilities'.
Since 'sense' is mainly represented by prudent Elinor, her actions support this theme in a greater level. For example, the death of father, Henry Dashwood caused them utter pain.
They gave themselves up wholly to their sorrow, seeking increase of wretchedness in every reflection that could afford it, and resolved against ever admitting consolation in future. Elinor, too, was deeply afflicted; but still she could struggle, she could exert herself.
Here, 'they' means Marianne and Mrs.Dashwood. They cry aloud over the death of thier father, continously, toally giving in to their sensibilities. Contrastingly, Elinor could exert her grief-- the readers begin to realize the worth pertains to 'sense' along with the admiration of Elinor.
Another action which support this theme is their beheviours in desperate situation. Elinor feels downhearted when she lears Edward's secret engagement with Lucy Steel. But she does not want to let others upset learning this. Elinor keeps this a secret and hides her pain.
...her good sense so well supported her that her firmness was so unshaken and the cheerfulness of her appearance was so invariable.
Moreover, her actions like helping Lucy despite of her personal grief, and the concealment of a heart-breaking information for the sake of the family happiness exemplify the theme, "sense".
On the other hand, Marianne, when she knew Willougby's infidelity, totally gives into her emotions. She writes letters, cries out loud, and suffers with fever that nearly takes her life. These actions support 'Sensibility', thematically.
Not only these two characters, but the minor characters' actions too so well support this theme. If you read and re-read the book, you will find a lot of actions of these fictional characters which aid this theme.