If one's love is not returned can one continue to love ?

Sure, but it's a little sick.

Alikimr, I think that love, including romantic love, cannot last without both inputs and outputs. That is to say, it is a product of an on-going exchange of loving expressions. A person can, however, love a deceased spouse even though that spouse no longer exists--the memory does.
A little sick, Lash? Keep in mind that the Greeks called love the divine madness.

A person can (perhaps misguidely) continue to love the person that they first loved - despite the fact that the object of their love might have changed.

My wife and I have changed throughout our life together, in some ways for the better and in other ways not--from my perspective, of course. But I love her now more than I did when we first married--I was mainly "attracted" to her looks then, now it's to her personality. That comes from a life of exchanges

There's also what the person "is". Despite everything, you can continue to admire/need/acknowledge what the person is to you.

Whenever I wonder about such things, I recall the words of Emily Dickinson:

Emily Dickinson - She rose to His Requirement -- dropt

She rose to His Requirement -- dropt
The Playthings of Her Life
To take the honorable Work
Of Woman, and of Wife --

If ought She missed in Her new Day,
Of Amplitude, or Awe --
Or first Prospective -- Or the Gold
In using, wear away,

It lay unmentioned -- as the Sea
Develop Pearl, and Weed,
But only to Himself -- be known
The Fathoms they abide --

One could reverse the gender in this poem and still have it retain its meaning.

Love is mutual, not onesided.

Affection returned is "love". One-sided affection is "worship".

Good, Noddy. I recall--painfully--a failed love affair in my youth. We were both physically attracted to one another but horribly mismatched in terms of personality, values and interests. She was more realistic than I and left me. I suffered for a while thinking that I had lost something very important. After a while I was greatful for her realism. But I DID sort of "worship" her for a while. THAT was sick in a way, but I think the sickness was normal or at least understandable.
We live and learn. No learning without the living.

Most love, I think, is love of self; if you truly loved another person, you could be happy even if they were with someone else, as long as they were happy. Most of us, perhaps all of us, are incapable of this degree of, for lack of a better word, altruism.

Our love -our insecurity, our loneliness, our incompleteness- requires the object to love us in return, or else.

Every step you take, I'll be watching you.

**

JL, Noddy, not ever--EVER in my life have I worshiped anyone. That's as honest as I know how to be.

Greyfan, perhaps.

Bram, you just reminded me of a song...................................................

There is infatuation with the stranger, such as a movie star, in which the actual character of our "love" is unknown to us. This is self love most pernicious, and not what I was thinking of earlier.

...

Can't say it enough times---there are only two emotions, love and fear.

Now to lighten up all this unrequitedness:

Artist: Lyrics
Song: Falling in love with love Lyrics

I weave with brightly colored strings
to keep my mind off other things;
So, ladies, let your fingers dance
and keep your hands out of romance.

Lovely witches
let the stitches
keep your fingers under control.

Cut the tread but leave
the whole heart whole.
Marry maids can sew and sleep;
wives can only sew and weep!

Falling in love with love is falling for make believe.
Falling in love with love is playing the fool;
Caring too much in such a juvenile fancy.
Learning to trust is just for children in school.

I fell in love with love one night when the moon was full
I was unwise with eyes unable to see.
I fell in love with love, With love everlasting,
But love fell out with me.

And that's one man's version, but there are several.

If she be not fair for me,
What care I for whom she be?

I see you guys have also lived.

I don't think so, for long. Love is a process, to me.

Love is oddly practical, it's a product, needs feeding, sort of like bread rising.

or growing and tending a garden, year after year, after year, after year...