Don't poison your attitude with complaints and gloomy pessimism of others; be aggressively and proactively positive. Proverbs 23:7 states, "For as he thinketh in his heart, so is he."
When we let the "small stuff" get to us, it can affect our entire mood and even change the way we interact with others. This can cause negativity to spread, just like a virus. Give that issue to God, be vigilant and protect yourself from negativity.
Finally, find delight in the little things, and you'll be pleasantly surprised at how delightful the big things turn out to be.