The "Days of Doubt" are often felt after you have made a big decision in your life, one that causes a turning point, and sends ripples of change throughout your life. The initial high point of excitement and anticipation of great things begins to wind down, and in trickles the very common momentum stopper; the "WHAT IFS". ("Trickles in" may be too light of a description of them though, as I've experienced them in an "O-My-God-whatdidIjustdo?!!!" mental charlie horse that leaves me desperately wishing for a delete button! )
So how do we deal with the days of doubt? The first thing to do is be aware that the doubt creeping in and stealing the show is just fear of the unknown, of change, and of new experiences. Know that the fear is just a thought in your mind and you have the power to change your thoughts. Next, remember to Breathe deep calming breaths while saying to yourself "All is well, and all is perfect because I choose it to be"
And last, be kind to yourself; You have just decided to move out of complacency and predictability and that choice is scary enough on it's own. Think, therefore, of the wondrous new adventures you are going to have, and have faith that everything is working out perfectly. Chase the fear away by continually focusing on your new dream, and by carrying the belief in your heart that you are meant to enjoy your life in this way, and not in mediocrity.