The above posts have some great insight and I also will say basically the same. Its about the journey NOT the destination. Hunting means different things to different people. In reading your post one REALLY great things stands out--it says allot about you and your true hunting integrity.
It says you have a true inner honor and integrity that is instilled in you that allowed you to simply "put-on-the-brakes." Yes it was a trophy in your minds eye HOWEVER--your experience and that inner voice allowed you to know--things simply were not right. You knew that taking that shot was NOT right because as you stated--"it was iffy"
What that says about YOU is that you have respect for yourself, fellow hunters, and the game you pursue.
DO NOT have remorse--reflect on the fact that you did the right thing. Be happy about that because I for one have my hat off and my hand extended to you and will say:
Good judgement call by you and what the sport of hunting truly needs are folks who have that inner voice that "puts-the-brakes-on", and makes them stop and truly ask themselves--"Is this right?" "If I take this iffy shot, and it all goes wrong-can I live with the outcome?"
I can tell you my good man--I have been there--have NO regrets because if you would have taken that shot--knowing full well things simply did not feel right--you knew full well things were not adding up to make a good ethical shot.
Think how you would have felt after the shot when it all went south--long, frustrating tracking job with no recovered buck of a lifetime---yeah--that's as sour memory and you would have that haunting you--going over it in your mind forever--regretting the whole mess.
Instead you can smile and say to yourself-"Yeah-I did the right thing-it was a great hunt that day."