Discover who you choose to become.
It takes a lot of heat and a really, really long time period to transform a piece of coal into a diamond. Similarly, you can think of your spiritual mission as this commitment to stick it out no matter what; and it is this determination, the resulting pressure of the clashing forces and the heat of the moment that form your character.
The spiritual traveler knows that where there is a will, there will be the WAY to lead you along. However, this journey is not about who you think you are, it is about your discovery who you choose to become as Allan Schnarr puts it so well. It is about the blocks in the way that will mold the "you". Your character in the end gets formed in response to all the choices you are making.
Will-power and good intentions are overrated. No-one can run for long stretches of time on will-power alone, no matter what all the good-sounding self-help books might tell you otherwise. Purpose gets you places, and the WAY will make sure that you have just enough will-power to make it work while allowing you to burn a lot of passion and some unwelcome karma in the process.
Ultimately, however, it is not "character" we are after. We want to be united with GOD. Do not confuse a worthwhile spiritual mission with sacrifice. Let the WAY remind you day by day of your purpose, adjust accordingly, and character and SELF will merge naturally.