The most fertile ground in mindful practice, in terms of what may grow, is in the place where your irritation lives.
It's easy to appreciate a nice person, or good weather, but can you shovel appreciation in a driveway of snow, or experience love for your partner when they do the irritating thing they ALWAYS do?
This article by Jaime Robeck for the Mindfulness Bell newsletter is a good practice roadmap that tracks some thoughts as they progressed from ongoing irritation, to eventual appreciation.