To Hashem is the Heaven and the Earth - this is amazingly depressing. Please join me, if you're able, in the Behab fasts coming up starting this Monday. When the Temple stood, a sin offering was given and we would burn only the fat and the blood. Because of our sins, the Temple lays in ruins. However, we still have free will and are able to obstain from food and drink.
Reb Moshe Feinstein ZT''L writes that when he was growing up, these fasts, held on the Monday, Thursday, and Monday after Sukos and Pesach were ta'anit tzibor - meaning all the Jews did them. Nowadays, he concludes, you have to make it a ta'anit yachid (only you are fasting).
However, our achdus is sure to be heard in heaven. I encourage all who are strong enough and won't be negatively affected, C''V, to ask your rav for permission to fast this Monday and take it from there in terms of Thursday and the next Monday. If you desire to do so, in your shmone esrei of Sunday's mincha, you must mention this intention.
All the best and may G-d Almighty lead us all back in this, the year of hakel, to Israel forever with the Temple standing proudly in its space and the world experiencing for the first time, world peace and abundence for all of its inhabitents.