Although some in Zen and other practices claim it can be a constant thing, most of us normies rely on mindfulness as a reset mechanism when needed. The key is to develop our own method that fits our personalities. When I feel my day is becoming overwhelming or depressing, I can do a mental reset to re-ground myself in reality, then get on with my day.
Soon after I started my addiction recovery program, I started traveling in the engineering field service biz in power plants, paper mills, etc. and often found myself mentally overloaded during big plant outages. I then learned a trick of going into a relatively quiet place such as a restroom alone and just doing a repetitive meditation to quieten the multiple committees in my brain. That simple activity got me through some very tough spots.
One technique along that line is to discover a brief "mantra" that is peaceful to the individual, then repeat that line over and over until you feel relaxation coming in. For example, one of mine is "Peace on Earth, good will to all". You can also print longer ones and post them around your home to read when needed, such as this one I borrowed from a meditation book:
"May I be filled with loving kindness.
May I be well.
May I be peaceful and at ease.
May I be happy."
Good luck in finding your own way!