i don't go all out when i spar, but i learn what could have worked had it been an all out situation. like with the elbow to face. i won't go implanting my elbow into anyones jaw, but in sparring, if i'm in the right position, i don't throw it, but i know that in that instant i could have used my elbow. when i shadowbox later, and work on the weaknesses i had during sparring, i also work on doing that exact scenario again (where i could have used the elbow), but this time i throw the elbow full force.
so hold back in sparring, but see the opportunities. and shadowbox full force later.
one of my kf brothers will throw the elbow in sparring, but stop an inch before contact. this shows the other guy, "look what you almost ate". i don't agree with this tactic, cuz it means you have to stop your power which may create bad body habit if you spar alot, and it shows a need to show the other guy, "look, i had you". i see that as a bit of an ego thing. i don't know how other schools are, but i have quite a few egos in my school who take sh!t personal, so it's better for me to not even go there, and practice full force on my own.
only gin and tang guzzle out a rusty tin can, me and this mic is like yin and yang