Why did Li Shimin leave Qin Qiong and Weichi Gong at the door when he slept?

We heard in The Romance of Sui and Tang Dynasties that Li Shimin asked Qin and Weichi Gong to watch the door while he was sleeping. So why on earth? Is there something hidden in this?

Every emperor's road to the throne is covered with blood. They all killed too many people on the battlefield or in the imperial palace. In her later years, Wu Zetian often had nightmares, dreaming that many people killed or framed by her came to seek their souls. I think too many people have been killed, and they are easy to believe in ghosts and gods in their later years, so they are afraid that people who have been killed by him will come to him, so they have nightmares and need Qin and Weichi Gong to guard his palace door and let themselves sleep peacefully.

"The Romance of Sui and Tang Dynasties" said: "Li Shimin, Emperor Taizong, killed countless people in the process of achieving imperial industry. After he acceded to the throne, he was in poor health and had restless dreams at night. Li Shimin is afraid of it and can't stand this torture. He called all the officials to discuss the matter, so Marshal Qin Qiong and General Weichi Gong were armed to the teeth and guarded at both sides of the palace gate every night. It can also explain that Emperor Taizong killed too many people when he was young. After all, he also killed his younger brother and forced the palace, so he often had nightmares in his later years.

There is also the influence of feudal superstition, which thinks that people will be weak in yang when they are old, and it is easy to attract ghosts, so I think this psychology will also have a certain impact. So he will feel uneasy when he sleeps. He needs Qin and the two of them to guard in front of the palace.