Or we do not perceive the opportunity to give a blessing.

This is true very often, especially in the closer and more tender intimacies of life.

We do not recognize the heart-hunger in our loved ones, and we walk with them day by day, failing to help them in the thousand ways in which we might help them, until they are gone from us and the door is shut.
Then all we can do is to bear the pain of regret, having only the hope that in some way in the life beyond, we may be able to pay--though so late--love's debt.
"How will it be When you at last in heaven we see-- Dear souls, whose footsteps in lost days Made musical earth's toil-worn ways, While we not half the loneliness That bound you to our side could guess?
Where angels know your footfall we Are fain to be.
"We never knew-- So heedlessly we walked with you-- The drops we jostled from your cup, That spilt, could not be gathered up; We might have given you foam and glow From our own beaker's overflow; Ah! what we might have been to you We never knew.
"We might have lent Such strength, such comfort and content To you, out of our ample store; We might have hastened on before To lift the shadows from your way, Darkened, ere noon, to twilight's gray; With earth's chilled air love's warm heart-scent We might have blent.
"Dear, wistful eyes, Ye haunt us with your kind surprise, Your tender wonder that a heart Should thus be left alone, apart, So loving, so misunderstood By us, in our self-centred mood: Alas! in vain to you arise Our longing cries.
"Oh, will you wait For us beyond the shining gate?
Though lovely gifts behind you left, We want yourselves; we are bereft.
From your new mansion glorious Will you lean out to look for us?
Shut is the far-off, shining gate-- Are we too late ?" These are but illustrations.

The same is true in all phases of life.
Every day doors are opened for us which we do not enter.

For a little time they stand open with bidding and welcome, and then they are closed, to be opened no more forever.