Or you can rely on common sense.
I can't disprove the existence of a monster in my closet, but I can deduce it based on what I know about the universe.
But truthfully, we aren't talking about and brushing off life at all, what we are really talking about is whether the specific deity of the Christians, Jews and Muslims exists.
My own feeling is very close to the thoughts posted from Stephen fry above. I used to be very strong in my faith. Little by little it was chipped away at by the circumstances of this world. Then one day it hit me. There either is no god, or he's a huge asshole.
If you don't mind I'd like to address that. I think that this is a common thought that comes up a bunch. I honesty think that it is based in really weak theology, which makes it easy to disengage from Christianity.
Mainstream Chrisitianity in America is generally screwed up IMO. Lots of the discussions have been turned towards defending or creating hot bottom issues, which is really sad. I think the huge distraction is all of these issues that Christians have been sucked into by their lack of real faith or just plan ignorance.
Anyhoo, your concerns are pretty easily explained.
1. God gave dominion and authority of the earth to man in the beginning. In other words, create your own destiny and do what you please. Man is the boss.
2. Man gave it back. Hence "the fall."
3. Now here's the part where most don't have God understating - Jesus came and let man have dominion over the earth restored to man. Christians generally don't understand that these days becaus we are too focused on gays or whatever.
How does that apply? It is up to us. The promise was restored to believers through Jesus to live freely. What have believers generally don't with that authority? Misused it. So, if life is kicking your ass you are living in the world that we created and its natural consiquences.
Lots of folks like to preach really stupid stuff like God is pouring out His wrath on us, blah blah, Katrina and all of that. That is so far of base theologically...it drives me crazy. All of the wrath was poured out upon Jesus on the cross. God simply lets us do on the earth what we want. That is pretty much why you see life sucking so bad at times.
If you continue to sin you will eventually get burned. It had nothing to do with wrath. It is much like what we see in our own children. Eventually you let them go. Teach them the right thing and let them decide at some point in their lives. Now, if they turn their lives to crap and go to jail or whatever does that mean that you are an asshole as a parent? Not at all. It just means that we all decide to do what we want.
I don't know if I made any sense at all. There is much more that I could add but I'm sure that leaves room for enough discussion as it is.