I learned from him that we shouldn't keep connected any Dapps for a long time. It would drain wallet funds after a certain period. Always disconnect your wallet even if you connect for any reason. Don't just leave it as it is. Hackers have powerful tools to trace you and drain your wallet. Don't give that chance.
This is valuable information for newcomers. Also note that you should never forget to check all the details before authorizing any transaction in your Metamask. Also note that an incoming transaction to your Metamask address does not require any action. After using Metamask, I always disable connected Dapps under "Connected Sites".