For reasons I will exclude, I will never be able to marry the young woman whom my heart will always belong to. I also feel called to a vocation. Can I pursue this vocation, even if I am in love with her but accept that we can never marry?
Allowing yourself to become romantically fixated on one particular person to such an extent that you refuse to open your heart to anyone else is spiritually unhealthy and dangerous. Since you have excluded marriage as a possible vocation, I do not know which vocation you might have in mind. I can only say that any vocation director you consult will very likely tell you that you must resolve your inappropriate feelings for this person before you can hope to fully open your heart to God.