Promises

Does anyone here have any personal code of ethics when it comes to promises?
Some promises can be seen as unreasonable to be expected to keep, and many break their oaths at these points, while others go to any length to keep their word.
Should certain people be expected to keep or break their word over others?
For example some might say it is honorable for a police officer to keep their word to a criminal, or that it's not inherently dishonorable for a spy to falsely swear allegiance to an enemy nation for the good of their homeland. I'm curious where most people draw these lines.
Some promises can be seen as unreasonable to be expected to keep, and many break their oaths at these points, while others go to any length to keep their word.
Should certain people be expected to keep or break their word over others?
For example some might say it is honorable for a police officer to keep their word to a criminal, or that it's not inherently dishonorable for a spy to falsely swear allegiance to an enemy nation for the good of their homeland. I'm curious where most people draw these lines.