The straight and narrow refers to a path, or state of being, that is considered the ideal. If one is on the straight and narrow it means they have not swayed from their path on the journey to their destination be it emotionally or physically. But life is rarely straight and narrow and often we are bumped off course through our own actions and attitudes and sometimes through no fault of our own.
Rarely does a person determine a goal and shoot arrow straight at it; Yes, they may start out that way, but there's always an obstacle to get around, overcome or shift.
When I push forward at my goals I always build in contingencies and understand that I may not be able to drive straight at them. That's why I build in a few check-in's along the way, just to re-evaluate and give myself the opportunity to reassess and adjust where required.
My straight and narrow is more a line that heads in the right general direction but sways left and right of the true-line as I adjust, overcome and adapt to changes along the way.
None of us can control the wind, however we can adjust our sails accordingly.