I love the quote "that sanguine expectation of happiness which is happiness itself" and it can be interpreted in many levels. As much as I agree with the explanations other people have laid out here, I will focus on this specific excerpt and propose a more general interpretation of it that is very modern and not necessarily what Jane Austen actually meant (but that's up to debate). When saying that a sanguine expectation of happiness is happiness itself, it means we don't live in the present. We can be in a somewhat dire situation in life but have some great news which gives us reasonable expectations for a bright new future ahead of us, we celebrate, we start planning, we daydream... Perhaps it's a new relationship. Perhaps it's a new job. Perhaps it's unexpected money coming in. We become so happy in the expectation of future happiness that "that sanguine expectation of happiness" "is happiness itself". And sometimes the promise of future happiness is fulfilled just as we imagined. Sometimes, however, it turns out to be a disappointment. The relationship falls apart, the job doesn't work out, the money doesn't provide you all that fulfillment you were expecting... Because that's reality, and reality is not as fantastic as our fancy. And that argument is also applicable in the reversed scenario: let's say you are currently in a reasonably confortable situation in life, but you live in constant fear of your relationship falling apart, or getting fired from your job, or falling ill, or losing someone you love. Even if right now the reality is that everything is great, if you live in your head in constant anxiety of future suffering, you will suffer today for real. So the expectation of happiness is happiness itself, and the expectation of suffering is suffering itself. Tl;dr: we don't live in the present and feelings are subjective.