Observing Sawm on Mondays and Thursdays is not restricted to Rajab or Sha'ban, rather it is a Mandub (commendable) act during all the months of the year. It is also permissible for whoever is in the habit of fasting them all year to observe fasting them after the fifteenth of Sha'ban, even if one of these days coincides with the Day of Doubt (so called because there is doubt concerning it - is it the last day of Sha'ban or the first day of Ramadan?), for the Prophet (salallaahu 'alaihi wa sallam) said:
Do not observe fast for a day or two days ahead of Ramadan, except a person who is in the habit of observing a particular Sawm; they may fast on that day.
(Agreed upon its authenticity by Al-Bukhari and Muslim)
Subhanak Allaahuma wa bihamdika ash-hadu anlaa illaaha illa anta astaghfiruka wa atubu ilayk
If I said anything correct, then it is from Allaah (subhanahu wa taa'ala), and if I erred, then that is from me and shaytan.