The idea that one should seize the moment (carpe diem) because life is short is a strong one in the play. The play’s songs, in particular ‘O mistress mine’, touch upon this idea.
Twelfth Night: AS & A2
Many characters could be said to act ‘excessively’ in the play, from Orsino’s exaggerated romantic speeches, to Sir Toby’s drinking and singing. Such ‘pleasure’, Feste says, will be ‘paid’ for in the long term, both literally and metaphorically.
There are several types of love in the play: romantic love (e.g. Orsino and Viola), self-love (Malvolio, and perhaps others) and familial love (e.g. Viola and Sebastian). One can add to that, ‘unrequited love’ (Antonio, Sir Andrew and perhaps even Malvolio).
Characters conceal themselves both literally (i.e. Viola and Feste) and metaphorically (Orsino’s exaggerated love for Olivia) throughout the play. These disguises suggest ideas about the self, and the nature of desire and truth.
The idea of ‘madness’ in various forms occurs throughout the play; from the ‘mad’ behaviour of Sir Toby which enrages Malvolio, to the latter’s own strange behaviour in front of Olivia, and his subsequent incarceration.