Mourn Yerushalayim in Galut
Jews who are living in Galut by their own free will and have no desire or will to move to the Land of Israel can´t mourn Yerushalayim in an honest way. You can compare it to somoen crying out for a nice steak at a vegan restaurnat. The only way to be able to mourn and feel what we are missing is by living in the Holy Land.
Check out my thoughts about below
Have a meaningful fast