Mindset is as important, and can be more important than any other single factor. The most effective mindset for an individual will vary from individual to individual, and depend on their personality. Whatever allows the person to act and focus on the tasks at hand is the correct mindset. Some need anger to act, some need a sense of resignation to overcome fear, some need to depersonalize the target, some need to make it personal, etc… everybody’s different. There’s no mindset that works perfectly for everyone, and some people are unable to achieve some mindsets.
Keep smiling ... it'll just make 'em wonder what you're up to...