What were some of the obstacles in building the Taj Mahal and how did this affect the reign of Shah Jahan?
One of the obstacles in building the Taj Mahal was the nature of the project itself. Intended as a tribute to the untimely death of his wife Mumtaz Mahal, the building had to be memorable in design as well as construction. This is why Jahan insisted that the shrine would be constructed solely of white marble atop brick. Doing it this way required the skills of architects from all over the Mughal empire due to the precise care involved in the design and building. One such traveler was Ismail Khan (Afandi) from distant Turkey, known as a designer and builder of domes for the Ottoman Turks.
There were also goldsmiths from Lahore and a calligrapher from Shiraz in Iran. The materials also came from distant areas, with the marble from Rajasthan and many inlaid precious stones coming from distant areas in India, Ceylon, and Afghanistan. The design was likely more challenging than the labor of the construction, as the nearby river assisted in bringing the marble to the site rather than over land, as in the case of the Great Pyramid in Ancient Egypt.
While Mahal's death no doubt affected Jahan deeply as a loss, he chose to honor the loss through architectural passion, be it in the mausoleum, the Red Fort, or suchlike. In this way, the untimely death could be said to have strengthened his resolve to rule by making contributions that would endure far beyond his life. The shah was known to be a consultant to the design and construction, but it is unlikely that he was personally involved beyond commenting on the design and regular inspections during the building. Given the Taj's elaborate design, anything more would be unrealistic, even though Jahan's reign was not overly consumed by conflict (clashes with the Ottomans and Safavids).