Having a questioning mind is a good quality to have.
The Reddit news feeds allows me to see at a glance what is going on in the world, yesterday there was a report about the discovery of pyramids in the Antarctic. It would be history-changing if this discovery was true, though I questioned and dug deeper. Every source with the pyramid story dealt with UFOs and lost civilisations, a red flag that the story was fictional. The reports lacked substance, failing to mention names or organisations connected to the so-called scientific expedition. No mainstream media reported the discovery. My questioning revealed a potential fraud.
As a historian I will question everything I read, plus all my sources, as I delve deep to the authentic reality. Getting to the truth when it comes to learning about my ancestors is important to me. Edward Williams was an important expert on Welsh literature in his time, but he created forgeries, so I dismiss everything related to him as a useless source. Geoffrey of Monmouth, used in his work real sources which he added to with fictional narrative, I use him as a source of context against other sources. Julius Caesar is a useful source of first-hand experience, as he directly dealt with the Celts and Druids; I take into account Caesar’s bias to impress the Roman citizens.
Even a credible academic source makes mistakes, but you need to know your subject to see it. The Colchester archaeologists concluded that a series of spectacular Celtic graves they found in Colchester was once a farmstead converted to grave site based upon a cooking area they found; I rejected the conclusion, as many ancient Celtic funerary sites contain cooking areas for feasts to commemorate the deceased.
Question everything. Sources often are false, error or prejudiced.