For me there are few things I consider:
First when ever I consider shooting a safety I first decide which shot is more difficult, the safety or making the ball. While safeties are necessary you are giving the table to other player and taking away your chance to win. So you have to not only consider the cue ball control you need to play safe, but you also have to consider what you opponents action will be after you leave them safe.
This can be very complicated unless you know your opponents ability, I understand that there are lockup safeties but in most cases a decent player can kick or jump out of a safety shot. So yes I think that before you consider playing safe you give the above information I have offered some thought, and if you do this many times you may find that playing safe is NOT better than shooting the shot Especially For The Game Ball
Second as far as putting your effort into to thinking about playing safe or the actual mechanics of playing the safe in my opinion there is not much difference. I have found at least with myself that in most cases if I can not visualize the shot when considering it, I am not going to make that shot. I do not know about others, but when I am shooting any shot I actually picture the shot in my mind while stroking it. This statement includes not only the ball traveling into the portion of the pocket I am aiming at, but also the entire path the cue ball will take until it stops. This is how I gage my speed, the English or lack of that I am going to use, and the type of stroke I think is necessary to accomplish all of the above.
Hope this helps.