In my opinion, there is no way to answer this question. Sorry.
I was in Paris just one month before the attack, staying just 2 blocks away from Le Petit Cambodge in Belleville. Then I was in Istanbul in December, again, just one month before the attack, staying 2 blocks from Sultanahmet’s main square.
In between the Paris attacks and my visit to Istanbul, my loved ones asked me if I was sure that going to Istanbul was a good idea. I replied, “I’m still going”. The truth is, I didn’t really know if it was a good idea, and although I did consider my options, there was never any real possibility of me canceling my visit to Istanbul. Today, I don’t have any mixed feelings about having visited these locations when I did, and I would go back to both cities in a heartbeat. And yes, I realize how lucky I am, and I am grateful.
For me personally, I decided that I didn’t want fear to control or influence my decisions. That is no way to live. The best thing we can do right now is not let the violence and terror (even if by our own volition) take away our freedom to enjoy life. Take a cue from Paris. Everyone must decide for themselves, but this is what I have decided, for me.