Great Happiness will come to pass in the Dasa or Sub-Periods of:
1. Navamsa(D9) dispositor of Lagan Lord
2. Planet posted in the sign together with the 7th Lord.
3. Navamsa(D9) dispositor of 5th Lord. We can also check for 9th lord Navamsa dispositor.
4. Dasa of the star lord of Lagan(Asc) gives rise in career.
5. Dasa of the star lord of Yogakaraka will also give rise in career.
Expect Problems in the following periods:
1. Navamsa dispositor of Saturn
2. Navamsa dispositor of Mandi
3. Navamsa dispostor of the planet in whose sign the 8th lord is placed.
Weakest of the above three will destroy the native happiness.
Also, check for these periods :
1. Dasa of star lord of natal Ketu may give misfortunes.
Judicious use of the above technique should be done. Sages have given us hint and they had faith that only the intelligent or the one destined to use the particular rule will be able to decipher it. I believe that every rule written in Classics is true, it is the astrologer who is not able to decipher or use it correctly. They were not fools to right such rules.
Of course other rules may apply when you apply these rules.