A double-digit lead against an incumbent president this (relatively) close to the election is very bad news for said incumbent. And very good news for everyone else.
Biden is very sensibly not interrupting when Trump is making constant, unforced errors, making himself look worse and worse; the Lincoln Project is getting under Trump’s skin and hopefully reaching at least some Republican voters; and the BLM protests and Covid-19 keep people energized to do something about the orange fuckwit in the White House.
Now, complacency and overconfidence are dangerous. But constant anxiety and expecting the worst is also bad for you, and allowing yourself to feel a glimmer of hope is important lest you burn yourself out. It’s okay to look at the polls and accept that they’re a good sign. 2016 was seriously traumatizing to a lot of Americans, in the literal, for-real psychological trauma sense. But 2018 and the various special elections have shown that 2016 is not the default, but an anomaly.