I rather liked Paul Greenberg's Things I Should Have Learned
Don't worry so much. Heck, don't worry, period. Worrying is an attenuated form of atheism. Do your best and then let Somebody Else handle it.
"Step lightly; do not jar the inner harmonies." -Satchel Paige.
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Always show good will. If it is not reciprocated, nothing is lost. If it is, celebrate. Contrary to Machiavelli, it is better to be loved than feared, at least in personal relations. Nations are something else; they have interests, not friends.
"Life is a narrow bridge. The most important thing is not to be afraid." -Reb Nachman of Breslov, who also said: "If you believe you can damage, then believe you can repair."
Instead of contemplating our sins, why not make up for them? It can be done. That's what We the Guilt-Ridden forget. Dickens' "A Christmas Carol" starring E. Scrooge should be read the year 'round.
Here's another gem from Reb Nachman: "Seek for the merit in others, even the tiniest shred. Then do the same in yourself."