Do you believe that a life of peace and harmony is ever possible for people?
If yes, can you describe how?
In theory, yes, it's possible. How I would go about achieving it:
1. Hand over all the keys to all the military installations to the UN, who will then destroy 100% of the nuclear missiles, decommission 90% of tanks, submarines and weapons, reassign 80% of the ships, aircraft and land vehicles for civilian use (rescue, emergency, cleanup and relief operations) and keep only a small standing army (international and fully integrated, of course) for intervention in local flare-ups.
2. Set up international courts of arbitration for outstanding disputes between peoples - the administration of each ruling to be done by a peace-keeping committee for the first five years; the committee than reports back to the court with recommendations for amendment - when it's working, the ruling becomes final. Then the committee hands over control to the local elected governments.
3. Disarm all repressive regimes and police forces that have a record of harming the citizens. Leave honest police forces in place, with all their crime-fighting capability, but take away their crowd-control equipment. Collect and destroy as many private weapons as can be done without riots; stop the retailing of new weapons and all ammunition.
4. Remove all clergy from political office and influential positions near government. Take away their privileges regarding money-collection, wealth accumulation, tax-exemption and property ownership.
5. Repeat 4. with the richest 0.01% of the world's population and the top 100 banks.
6. Abolish compound interest; write off all current debts. Confiscate the ill-gotten gains of above groups; hand over land and stationary assets to local governments;collect the liquid assets in an international fund to be used wherever most needed.
7. Now that governments don't have to spend most of their time waging war and serving the rich and godly, and have the wherewithal, they can get on with their proper job: taking care of the people who elect them, dealing with problems of energy and production and distribution.
Do I think humans will become sensible before they become extinct? Not for a minute.