Wagner reached a point in his struggling years when he felt pulled in too many directions. His letters to several friends describe the torment of multiple, diverse musical themes pulling his creativity in diverse directions. He decided to halt the composition of Siegfried almost in the middle of the Second Act to allow the growing theme of Tristan to develop. However, he wrote to Liszt's more than friend Marie Wittgenstein that Siegfried would not leave him, so he went back to the composition and completed the Second Act, freeing the hero and himself from the captivity of the dwarves and the dragon. Yet, he says, "Tristan would give him no peace..." while he was working on Siegfried reaching the point of following the forest bird. At this point the opera Siegfried becomes a set of bookends inside of which Wagner wrote and composed Tristan und Isolde, Die Meistersingers, and the Paris version of Tannhauser.
Interestingly enough, the two new operas are variations on the sacrifice theme that Wagner ubiquitously used throughout his creative works, only in these two works we discover the sacrifice is not made by a loving woman; rather, the sacrifices are those of older men who sacrifice their personal feelings for the sake of others. Schopenhauer and the Eastern philosophies echoed through Wagner's works at this time--the idea of unbridled will causing misery finds expression in both operas. Hans Sachs expresses Wagner's view of this quite clearly in the "Wahn, Wahn" monologue, which occurs the morning after the brawl between David and Beckmesser the night before.
