For Heaven only knows why one loves it so, how one sees it so, making it up, building it round one, tumbling it, creating it every moment afresh; but the veriest frumps, the most dejected of miseries sitting on doorsteps (drink their downfall) do the same; can’t be dealt with, she felt positive, by Acts of Parliament for that very reason: they love life.
Here's Clarissa walking to the flower shop one fine summer morning with the sound of Big Ben chiming in the background. In a classic example of Woolf's modernist prose, we have a character essentially creating her own world and letting the reader enter this world by means of an internal monologue.
As you can see by reading the quotation, it consists of a single sentence punctuated by colons and semi-colons. This is an indication not just of the stream-of-consciousness style used by Woolf and other modernist writers but also of Clarissa's sheer excitement at the joy of being alive.
It also reveals certain of the assumptions of her social class. In her unbounded enthusiasm for life, Clarissa even assumes that her joyful attitude is shared by the ordinary folk, the "frumps" and the "most dejected of miseries." According to Clarissa, happiness is something that transcends class; it belongs to anyone who can see beauty in the world around them.
She had a perpetual sense, as she watched the taxi cabs, of being out, out, far out to sea and alone; she always had the feeling that it was very, very dangerous to live even one day.
This quotation also tells us a lot about Clarissa's personality and about the human condition in general. Even in the midst of a busy London street, her soul feels lonely. She also feels vulnerable, and that vulnerability is represented by the undulating waves of the sea that threaten to overwhelm at any moment. Like everyone else, Clarissa is alone in the sea of life and must do whatever she can to stay afloat.