Safe? That depends. This particular spell is a set up for some nasty effects, mainly obsession.
When you do a spell to make someone "agonize" if they aren't thinking of you, you are specifically causing them to be obsessed. Now while that sounds all fine and good, obsession can lead to some very dangerous situations, including a person to have a "if I can't have you, no one will" mentality.
I am all for love spells, but binding someone to you is like caging them. You aren't allowing them to find happiness without you, you aren't allowing them to be who they really are. Usually, people look at that and say "Well that's ok. I love this person and I always will". Fact is...it really doesn't work out that way most times.
So let's say, 4 years down the line you no longer care for this person (it's very possible). You now want out of this situation, but you've tied the person to you so that they can't function or get away from you. You are their everything, whether or not you want them to be anymore.
And let's be honest, if it was a happy wonderful relationship that is supposed to withstand the tests of time..there really wouldn't be the need to bind them.