The period of the three weeks, going into details
Rabbi Chaim Vital, one of the main students of the Arizal, wrote several books on the teachings of his rabbi. Some of the books that he wrote are Etz Chaim and the Eight Gates, one of the Eight Gates is Shaar Hakavanot (The gates of intentions) that deals with the proper kavanot (meditations) that a person needs to have during the events of jewish life.
In Shaar Hakavanot, the Ari explains that from 17 of Tammuz to 9 of Av we have 21 days and that it is a very good custom for any one that is Baal nefesh (elevated person) to sit mourning on the destruction of the Beis Hamikdash. The mourning should be done after midday because we have a concept that after midday there is an awakening of the judgements and it goes also as it happened, the beginning of the burning of the Beis Hamikdash was after midday. Someone that is doing this custom is getting a big benefit to his being. Also the person has to continue (not to do only during these three weeks) making tikun chatzot at midnight.
If you feel that it is already too much, all the restrictions that we have according to the halacha plus doing kabbalistic stuff on top of that! Don’t feel bad, rabbi Shephard explains that there are people that their soul is connected to the destruction of the Beis Hamikdash, these people are susceptible not to feel good after midday. They could experience anxiety, sickness or just a sensation that something is not right; for them tikun chatzot after midday could get a physical and spiritual relief. And there are people like that today, there are rabbis that claim that tikun chatzot is part of the daily order of prayers while others do not make a big deal about it.
You might be asking yourself: then what do I do? So rabbi Shepherd says it has to do with from where everyone’s soul of each person is coming from. The main thing during these three weeks is to really connect to Hashem on a higher level, it is very hard to actually cry and feel something that happened so long ago. So in order to really reach higher spiritual levels we have to focus first on ourselves and the relationship we have with Hashem. We have to first mourn and rebuild our inner Beis Hamikdash so that we can continue climbing and begin to really feel the destruction of the physical Beis Hamikdash.
We have to remember that we are not crying for the physical building but to the connection the we lost with Hashem. When we realize, through the words of the sages, all of what we lost spiritually we should mourn even the whole year. May these three weeks be Ann opportunity to come closer to Hashem and to work on our flaws to become better jews.