I really don't think of love in connection with fear of loss.
We know for a fact that all of us are going to die therefore it's kind of pointless to be "afraid" of losing the person you love. If you are fortunate enough to have a lifetime relationship/marriage it's unlikely you both will die on the same day so it's pretty much a given.
If you are afraid of "losing their love for you" it would seem to indicate to me that you aren't fully immersed in the relationship or you have some doubts concerning their love for you. Maybe they have said or done something which indicated to you that they aren't as emotionally commited to the relationship as you.
Either way when it's all said and done the best way to enjoy life is to live in the moment.
"Worry does not empty tomorrow of its sorrow. It empties today of its strength." - Corrie Ten Boom