It's true.  We can have a desire to love someone in the future...and we can be glad that God helped us to love in the past, but we can't really sacrifice (that's the Catholic definition of love..it's the one that Christ gave us on the Cross) in the future or the past...the act of the will to love is only available to us in the present moment.

And that's why God doesn't want us dwelling much on the past or dreaming about the future...He wants us to love Him in the moment by serving someone near us.

My wife knows this...she understands that love is a decision, not mere shifting feeling.  Love is  a Yes, let it be done to me according to  your word (and will).