The analyses of a text #2

The narrator recalls his adolescence.
He is an apprentice for the lawyer Mr. Spenlow.
He is crazy for Mr. Spenlow's only daughter Dora.
He came to go out with her after his confession of love.
He is now writing to his best friend Agnes about his love affair.
His old nurse Peggotty's niece Emily fled with his another best friend Steerforth, leaving her fiance behind.

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Somehow, as I wrote to Agnes on a fine evening by my open window, and the remembrance of her clear calm eyes and gentle face came stealing over me, it shed such a peaceful influence upon the hurry and agitation in which I had been living lately, and of which my very happiness partook in some degree, that it soothed me into tears. I remember that I sat resting my head upon my hand, when the letter was half done, cherishing a general fancy as if Agnes were one of the elements of my natural home. As if, in the retirement of the house made almost sacred to me by her presence, Dora and I must be happier than anywhere. As if, in love, joy, sorrow, hope, or disappointment; in all emotions; my heart turned naturally there, and found its refuge and best friend.
Of Steerforth I said nothing. I only told her there had been sad grief at Yarmouth, on account of Emily's flight; and that on me it made a double wound, by reason of the circumstances attending it. I knew how quick she always was to divine the truth, and that she would never be the first to breathe his name.
[David Copperfield by Charles Dickens]
1. I'd like to know what "of which my very happiness partook" means.
2. And I'd like to know what "breathe his name" means.
Thank you in advance for your help.