don...
at the bigginig of my photography years aho, i had only normal lense on my pentax mx (i was still teen and had no money). i have learned to visualize on it and more than that i have learned to express with one lense. than i had the tlr (rolleiflex) which i loved very much. again with only one normal lense i understand even deeper how well i can work with only one lense. on the contax slr i had few lenses, but i found it so difficult to make serious works on it, and always when i was pushed to do serious work among all the lenses the plannar 50mm was the chooice. not that i have made bad pics with 28 or 85, but i felt much better when working with the plannar.
since then i have developed. i use lots of lenses. the choice of the lense for the job is upon my mood. for example.. if i am on the street and observe the street from the "outside = not really involoved" than i take a normal lenses. if i feel more involved i just go very close and i use a realy wide one. i dont really change during the picture taking. i just feel what i feel when i take photos and that way i choose the lense. the same i can say for everything, including studio works, nude, portraits etc.