Friendly Fire isn't friendly.
Suppressive fire won't suppress.
Recoilless rifles aren't recoilless.
If the enemy is in range, so are you.
You are not Superman (Marines and Fighter Pilots, this applies double to you).
If it looks like a good spot for an ambush, the enemy is thinking the same thing.
Remember Thermopylae? Where the Spartans were defeated because of an unguarded goat path that led to the rear flank? Yeah. Guard your rear flank.
Unfair fights are something only the losing side complains about.
You may be willing to die for your country, or your cause, but I'm killing to kill for it first.
No battle plan survives contact with the enemy.