I was thinking of titling this one “He who runs away, lives to fight another day”.
When searching a structure (this isn’t a military operation), don’t get into the mental rut of “NO RETREAT”. There is no hurry here, no need to be kicking doors, making dynamic entries and doing John Wu style rolls into rooms. Take your time and slice the pie. Clear what you can from a safe location.
Make your entry and immediately clear any area you couldn’t see from the outside.
Consolidate your position and begin to deal with any areas that require checking.
If you see someone, don’t allow the adrenalin to override your good sense. A small room is not the best place to deal with a possibly armed opponent. Especially if it’s possible that there could be a second guy behind that object.
If you don’t have to immediately use deadly force, SOMETIMES (nothing is set in stone here) it may be best to back out of the room to a secure area and call the bad guy out to you.