You deal with it by letting God/nature/karma/fate (whatever your life outlook prefers) take the lead. I sometimes have it, sometimes don't. I've tried to talk to my hubby about it and his only response has been "if it happens, it happens." Sometimes this frustrates me. In the end, though, that's the way it works best for most. As someone else said, you can plan until the cows come home and it will never seem like the right time. You can always have more money, more time, bigger house, fewer stresses...its a never ending cycle. If you're both mentally and emotionally prepared (as you can be as new parents not knowing what to truly expect), the rest typically always works out. You find ways. Its what you do as parents.
I guess the shorter answer is to stop battling your logic. The birth/baby process is illogical because its unique to a woman and brings forth a plethora of emotions, trials, tribulations, and joys that you just cannot reproduce in any other life situation.
My extra two cents, just knowing you want to try to plan speaks volumes for your readiness as a parent.