In Sonnet 29, the speaker changes from despondent to thankful.
The sonnet 29, titled 'When, in disgrace with fortune and men's eyes,' the narrator tells us how he envies somebody surrounded with fortune and friends, when he has none. He is quite depressed in the beginning, but as the sonnet moves on, we can see that the narrator grows happier when he thinks about his love, and he is thankful for her/him.