The expense of spirit in a waste of shame
Is lust in action: and till action, lust
Is perjured, murderous, bloody, full of blame,
Savage, extreme, rude, cruel, not to trust;
The first  quatrain  begins with a strong  declarative  statement that leads on to the subject of the negative consequences of lust.  “The expense of spirit is a waste of shame” is memorable and encapsulates the rest of the sonnet.
Sonnet 129