One of the chief complaints against the character of Duke Orsino is that he is more in love with the melancholy feeling of being in love than with Lady Viola herself. This is made clear from the very first speech of the play:
If music be the food of love, play on;
Give me excess of it, that, surfeiting,
The appetite may sicken, and so die.
Orsino is in a lover's mood but it is clear he likes being in this state. Even when Curio tries to distract him by getting him to go hunting, Orsino, love-sick as he is, can only pun cleverly by associating the hart with the object of his affections. It is interesting that he himself will not go to testify his love for Lady Olivia - he always sends messengers to testify his love, perhaps another indication that he likes this state of love-wrought excitement and almost does not want it to end.
In Act I Scene 5 we see Viola as Caesario delivering Orsino's speech. It is interesting that she does this in a way that makes Orsino's love treaties to be absurd. She starts off in a rather hackneyed fashion; "Most radiant, exquisite and unmatchable beauty" (hardly original), before stopping to verify who the lady of the house is. She also makes pains to stress the artificiality of her speech, which undercuts its persuasive power:
Most radiant, exquisite and unmatchable beauty,--I
pray you, tell me if this be the lady of the house,
for I never saw her: I would be loath to cast away
my speech, for besides that it is excellently well
penned, I have taken great pains to con it. Good
beauties, let me sustain no scorn; I am very
comptible, even to the least sinister usage.
Later, Caesario says again, "Alas, I took great pains to study it, and 'tis poetical". Viola immediately picks up on this in her response: "It is the more like to be feigned. I pray you, / keep it in." However, it is when Caesario says how he (she) would woo Olivia that Olivia is attracted to him - when she speaks her own original and non-practiced words, in one of the most romantic speeches of the play:
Make me a willow cabin at your gate,
And call upon my soul within the house;
Write loyal cantons of contemned love
And sing them loud even in the dead of night;
Halloo your name to the reverberate hills
And make the babbling gossip of the air
Cry out 'Olivia!' O, You should not rest
Between the elements of air and earth,
But you should pity me!
This unpracticed speech is from the heart, and infinitely more attractive than Orsino's studied and impersonal declarations of love.