Do bad times pass?

All times pass, as time is inexorable.  So as bad times are a proper subset of all times, I would say "yes."  However, because "bad times" are subjective, it's possible (perhaps even likely) that there is a continuous thread of bad times running through human history, and so it might be able to answer "no" with respect to the experience of the entire population.

I'm reminded of the anecdote of a friend greeting his acquaintance, who was particular about language use, with the interrogative, "So how is everyone?"  The acquaintance looked panicked for a moment, thought for a bit, and eventually replied, "Average."
Hell yeah!! But remember, you actually NEED them to come back too.
Just like, water tastes sweet after lime. you cant enjoy good times unless you have the bad to compare them to. GOOD and BAD are relative.

I am sure you know of people who are having a bad time because their corvette broke down. F#$%, i would kill to have my own corvette to break down!
Good and bad are subjective to your opinion. If your car bumps into a wall, its bad for you since you lose money, but good for the mechanic who gets business.

External conditions may remain the same for a very long time. A child born with a disease may carry it until death. So not every bad 'condition' will pass.

But the perception of whether one's time is good or bad will most definitely change. Human minds are quite dynamic. When overwhelmed by many bad things, the mind will look for some kind of silver lining in any cloud.
Yes. You just need the guts to hang in there. After that you will be stronger and will appreaciate life more.
Got really nice and simple quote here.
"NO matter how your day goes, the sun always rises the next day. You Get a fresh start." John Herrick
For us yes.
Do Americans have to get shots before going to Africa?

Whether or not you need shots will depend on the countries you plan to visit and how up-to-date you are on your regular vaccines.The CDC recommends Hepatitis-a and Typhoid for many countries. As Nneya Richards indicated they will also list specific vaccines for specific locations.

Why don't cell phones use 5v batteries?

Because there is no such thing as a 5v battery. The voltage of a battery cell is dependent on its chemistry. The voltage of the assembled battery is an integer multiple of the cell voltage.There is nothing special about five volts. The battery is not five volts, the components in the phone do not run on five