According to a recently published article in a German review, Wagner wrote a long letter to his sister Clara, explaining why Minna had left him, and making himself out to be as thoroughly misunderstood domestically as he had always been musically.  It is a long letter, but quoteworthy, the italics being mine: 

“MY DEAR CLARA:—­I promised you further information regarding the causes of the decisive step which you now see me taking.  I communicate, therefore, what is necessary to enable you to contradict various pieces of gossip, to which indeed I am indifferent.

“What for six years has kept and comforted me, and especially has strengthened me in remaining by Minna’s side, in spite of the enormous differences in our characters and natures, is the love of that young lady who, at first and for a long time, timid, doubting, hesitating, and bashful, finally more determinately and surely grew closer to me.  As there never could be any talk of a union between us, our profound affection took the sadly melancholy character which keeps aloof all that is common and base, and recognises its fount of happiness only in the welfare of the other.  From the period of our first acquaintance she had displayed the most unwearied and most delicate care for me, and in the most courageous way had obtained from her husband everything that could lighten my life.

“He could not, in presence of the undisguised frankness of his wife, do anything but soon fall into increasing jealousy.  Her nobleness now consisted in this, that she kept her husband informed of the state of her heart and gradually led him to perfect renunciation of her.  By what sacrifices and struggles this was attained can be easily guessed; what rendered her success possible, could only be the depth and sublimity of her affection, devoid of every selfish thought, which gave her the power to show it to her husband in such a light that he, when she finally threatened him with her death, had to abstain from her and had to prove his unshakable love for her only by supporting her in her cares for me.  Finally, he had to retain the mother of his children, and for their sake—­who invincibly separated us—­he assumed his position of renunciation.  Thus, while he was devoured by jealousy she again interested him for me so far that—­as you know—­he often supported me.  Lastly, when it came to providing me with what I wanted—­a house and garden—­it was she who by the most unheard-of struggles induced him to buy a pretty little property near his own.

“The most wonderful thing is, that I never had a suspicion of these struggles; her husband, out of love for her, had always to show himself friendly and unconcerned toward me.  Not a dark look must he cast on me, not a hair ruffled; the heavens must arch over me, clear and cloudless, soft and smooth must be the path I trod.  Such was the unheard-of result of the glorious love of the purest, noblest woman, and this love, which always remained unspoken between us, was compelled finally to reveal itself when I composed and gave her ‘Tristan,’ Then, for the first time her self-control failed, and she declared to me that now she must die.