If you think you failed, but learned an important lesson, you didn't fail. If you think you failed, and learned nothing, then you failed.
I always hang my bow or gun on the tree where I can reach it easily without moving much. As soon as I see a deer, I usually do one of two things:
1. If the deer is far off and/or approaching slowly, I hit them with the binos to determine if it's a deer I'm interested in or if I can see more coming behind the lead deer.
2. If they are close or approaching quickly, I smoothly reach for the gun or bow, keeping my eyes on them the whole time, only moving if their eyes are down or directed elsewhere. That way, if it's a deer I'm interested in taking, I'm ready to strike.
This all comes from experience of course, because I had something similar happen to me years ago. I had a doe approaching, and I locked my vision in on her, but didn't get ready to make a shot. At some point, I realized there's a buck following her, and I'm not ready. Now I'm trying to watch her, watch him, and move to get into position. Long story short, I'm watching him and trying to move to shoot. She busts me and blows everything up.
This was back in my climber days, so moving for a shot was a lot more involved. *Facepalm*
Since switching to a saddle, I can only remember getting busted once because of movement. I was new and still figuring everything out. It was drizzling, everything was wet, and it was hard to hear. I was gently swaying back and forth because I was bored and it was comfortable. I had a deer blow behind me and take off. Never even knew it was there because it unexpectedly approached in my blind spot, couldn't hear it because of the drizzle, and it caught me swinging back and forth. But I learned something that day, so it wasn't a complete failure.
You are not a hunter in the tree. You are the tree. "Be the tree"