Improv, like life, is made up as we go along: A never-ending exercise in living in the moment, playing off the moods and machinations of everyone who enters our orbit. And in the process, expanding our awareness of ourselves and the world around us. It’s a parallel exploited imaginatively by the hugely talented Mike Birbiglia, one of those high-falutin hyphenates who excels in all three phases of the filmmaking game. In “Don’t Think Twice,” his superb second feature, he both entertains and enlightens with his funny, often achingly realistic dissection of a Second City-like comedy troupe on the eve of destruction.

His storytelling is affecting, his acting top-notch and — most importantly — his direction is flawless as he balances comedy, drama and sentiment. He and his terrific ensemble thrive on the heels of sterling breakout work by the adorable Gillian Jacobs and a never-better Keegan-Michael Key (Who knew the “Obama interpreter” had this much range?) as a show-biz couple fractured by fame and ambition. They are the two featured players, but this is very much a team effort that underscores the idea that this familial improv group, a diverse collection of six individuals united by the love they share for their craft and each other. Like family, The Commune can be petty, jealous and often irritating, but they are always there for one another.

Birbiglia makes the most of those dynamics by making us privy to the array of reactions when a member of The Commune outgrows their ranks and advances to the Emerald City of improv comedians: The “SNL”-like “Weekend Live.” When Key’s lovably passive-aggressive Jack announces his good fortune to the gang he’s not met with smiles or effusive congratulations, but stunned silence, as his resentful “mates” turn an envious shade of green. It’s a moment that transforms a good movie into a great one because it lets us know that Birbiglia is going to keep it 100 in his depictions of characters.

Jack gives the others — his girlfriend, Sam (Jacobs); the wannabe graphic novelist, Allison (Kate Micucci); the too-trusting Bill (Chris Gethard); the slumming heiress, Lindsay (Tami Sagher); and Birbiglia’s vain, Peter Pan-ish troupe leader, Bill — plenty of reasons to vent, especially when he commits the ultimate betrayal: Stealing their material. More than anything, “Don’t Think Twice” is about that moment when your dreams go careening into the Jersey barrier of reality. As Bill says profoundly, “Your 20s are all about hope, and your 30s are all about how dumb it was to hope.”

Like that line, the movie is consistently funny and knowing, as Birbiglia structures his ode to the unsung comedians of the world like a romcom in which harmony is fractured and miraculously healed through love and understanding. But don’t take that to mean that Birbiglia is predictable.

He’s anything but. And his ability to get us to relate to his characters — as they come to the realization that life isn’t what you hope but what you make it — is so perceptive you swear he’s gotten deep inside your head.

As an added bonus, Birbiglia uses his stage to weave in a fascinating history lesson on the origins of improv and its sainted king, Del Close, the man who coached the likes of John Belushi, Gilda Radner, Dan Aykroyd, Tina Fey, Mike Myers and Bill Murray to stardom.

Birbiglia’s lovely film stands as a moving tribute to both Close and his contemporaries like Mike Nichols and Elaine May. But at its heart, it’s a big, fat juicy kiss to a profession that thrives on smarts while preaching never to overthink.

But as an audience, you can’t help but think, not to mention laugh and shed tears of sadness and joy over a story that deftly sneaks up on you before grabbing your emotions by the throat.

And that’s because comedy feeds off our pain and sorrow, making us smile widest when our spirits are lowest. Perhaps that’s why Jacobs’ Sam begins every Commune performance by asking the audience who out “there had a particularly hard day?” Whoever answers not only seeds the germ for the next skit, but fortifies the belief that life — in all its joy and despair — is indeed a laughing matter.

“Don’t Think Twice”
Cast includes Keegan-Michael Key, Gillian Jacobs, Mike Birbiglia, Kate Micucci, Chris Gethard and Tami Sagher.
(Rated R for language and some drug use)
Grade: A