Honestly, the most frequent reason I have for burning sage is if I had a guest over who had a foul attitude. Constant complaints/gossip? Totally burning sage over your chair as soon as you leave the house.
When our son moved out in a huff because we told him to get a job and he went no contact with us to teach us a lesson, after a couple of weeks I burnt sage under a photograph of him and within a day or two he reached out and contacted us so we knew he was alive, albeit still angry at us.
It's worth saying I never use sage alone. I always burn either dragon's blood or cedar with or after it. The metaphor I use for this is that the sage is like cleaning/prepping a surface for stain or paint, but the dragonsblood/cedar is what actually seals it and makes it stay that clean.
About once a season I do a deep cleansing of the apartment and go into each room, make sure the smoke gets into each corner, and walk clockwise through the house with a door open to chase bad spirits out through. Honestly something that formulaic doesn't completely align with my beliefs, but it's the way I was taught and it feels good to do, everyone compliments our house's energy so I keep doing it. After a cycle through the house with sage, I follow up with cedar. About once a year I'll go the extra mile and do the outer perimeter of the apartment building our unit is in, to cleanse and seal the whole building.
I do not repeat anything while I do it, but that's because my mind is blank when I'm doing it. If I do have a stray thought, I repeat my mantra. It's worth mentioning my mantra is not about protection or cleansing. My mantra is essentially "Lord of the Universe, destroy all obstacles in my path (including me, should I be an obstacle)". Tangentially it is both protection and cleansing, but I feel like it's both broader in scope and also more targetted in its meaning. Protection and cleansing beg the question of "from and of what", while "remove obstacles" is a bit more intuitive to the unconscious in my feeling.