You are tricking yourself into a dangerous illusion of recklessness being equal to deadliness.
If you mean deadly by meaning destructive, you can sure go ahead and blow up a frag grenade in front of the business office, and kill whoever is in the way.

If you mean deadly by being precise, you would never take a metal object inside a protected building. You would take out the exact man you want to take out, through a window of a neighboring building.

A man who has nothing, doesn't have to design escape plans.

Deadly is a term that can be freely played with. Sure, you can bring more death if you do not worry about your own life, but killing someone who is protected, is not necessarily easy. Your enemy may also have protectors who have nothing to lose, and they will react, and block your way to their best ability.
Your reckless destruction will detonate on them, as you engage them, and you will fail your task.

To bypass defenses, and not detonate on them, you must act with cunning and precision, and that requires considering losses. It demands natural fear as an instinct.

The fact that you are ready to die for your cause, does not mean you will succeed.
I would say, a healthy mix between courage and caution is required to truely achieve the goal.
A real maestro will know to mix these things in good proportion, when to jump, and when to hold still, and he will have the devil's luck.

The conversation is now shifting away, however, from the subject of killing missions to a slightly more sentient one:

What is better - to die for a friend, or to see a friend die.