Too Much for Man to Handle

This is what happens when a character goes into God mode, or at least experiences it in some way... and then realizes that he can't handle it: The knowledge of the inner workings of the universe overwhelms his mere human brain, the sheer power begins to burn out his mortal shell, he essentially experiences complete sensory overload on a cosmic scale. This can lead to suicide, insanity and sometimes other grisly results.

Related to but different from Things Man Was Not Meant to Know, as it is more the reaction/effects of said Things.

Examples of Too Much for Man to Handle include:

Anime

Tetsuo from Akira, whose immense power proves to be too much for him to control, causing him to suffer a horrific mutation.
Shiki in Tsukihime started seeing the lines of Death Perception after he got in an accident. Pro: He now has the ability to destroy almost anything by simply cutting the lines. Con: It makes him physically and psychologically sick, and being able to perceive death in such a way means his lifespan will be much shorter than a normal human's.
Happens to Edward in Fullmetal Alchemist Anime, when he came into direct contact with large quantities of unrefined Philosophers Stone.
In Ayashi no Ceres, once a ten'nyo/celestial maiden's powers are activated, her (or his) body starts to break down on a cellular level. It goes more quickly for some than for others, but it happens to all of them (save Aya/Ceres, who is ~~the protagonist~~ different).

Comic Books

In Secret Wars, when Doctor Doom gains the power of The Beyonder. Doom cannot even sleep for fear of accidentally destroying the universe.
- Doom seized the power of the Silver Surfer for himself, and it drove him mad.
In X-Men, this happens when Mastermind is given a glimpse of the universe as Dark Phoenix sees it after awakening her, and is reduced to a drooling, mindless shell.
- In the original Phoenix arc, Professor X said that when Jean Grey realized that the Phoenix power was too great for her to handle, she created a psionic circuit breaker in her own mind to keep it from overwhelming her.
In George Perez's Ares storyline in Wonder Woman, Ares was defeated by Wonder Woman showing him what would happen if he won with the Golden Lasso.
Detective Chimp had a reaction like this to the helmet of Doctor Fate.
All-Star Superman plays with this. When Lex Luthor gets the power of Superman, he breaks down and sees why Superman is such a good person. Someone with this much power would have to be a good person.

Fanfic

In the Twilight fanfic Luminosity, Addy escapes from imminent execution by telepathically broadcasting her entire lifetime's memories. She's several centuries old, and by using Aro's power has absorbed the memories of dozens of other vampires, some of whom are several millenia old. The escape... succeeds, to say the least.

Film

Happens to Irina Spalko in Indiana Jones and the Kingdom of the Crystal Skull, during the contact with the aliens, where she asks them for ultimate knowledge and her brain is essentially incinerated by the sheer amount.
In Forbidden Planet, Dr Ostrow uses the Krell brain-boost machine and it makes him really, really smart but he dies a few minutes later.

Literature

In The Wheel of Time, a Darkfriend once complains that he wants to have the full picture of what's going on, rather than his little piece of the puzzle. The Dark One gives the man a glimpse of the picture and it causes him to blackout from the excess of information he receives.
Ursault the All-Seeing from A Little Knowledge by Elaine Cunningbam has a great and clean prescience... and all he saw was one infinite maze of possibilities that change everything both for good and ill, depending on other possibilities, that... and so on. Since even his trained mind could keep only a very little part of the picture, this was more annoying than useful. Others considered him Mad Oracle because if he was asked for a prediction, it habitually dissolved into babble of endless conditional forks.
- In Elminster's Daughter Caladnei was bold enough to demand from Elminster and Simbul to talk the way everyone can hear instead of a mindlink they obviously used. It turned out that there were more than two participants and when Mystra agreed with this request, Caladnei (and everyone present) learned the hard way why exactly direct contact with deities is rarely used even by priests strong enough to do it every day. They were barely able to move after this fun—and she was nice.
In A Hat Full of Sky, this is the Big Bad's entire motive for possessing Tiffany. Possessing people helps it stave off the crushing pain of being simultaneously aware of every blade of grass or speck of dust in the entire universe.

Live Action TV

In the Doctor Who episode "The Parting of the Ways", Rose absorbs the Time Vortex to become the Bad Wolf and can't control its powers effectively.
- The episode The Long Game has a mention of futuristic computers - activated by linking to people's brains - having safeguards to prevent overload.
- At the end of Series 4, Doctor Donna's brain starts burning out from all of the Doctor's Time Lord experience, leading to a serious Downer Ending.
This is what happens in Stargate SG-1 if a mortal gets the knowledge of the Ancients/Ascended, either through an ascended being retaking mortal form without having his mind wiped (see the fate of Orlin after he tried to help contain the Prior Plague), or a mortal being subjected to an Ancient Knowledge Device. His brain literally cannot handle all the information and it starts to degrade his mind.
Joan of Arcadia once complained that she was tired of doing the oddball tasks God gave her without knowing the point of it all. God replied that people aren't meant to see the big picture, that they only see their part in it because that's all they can process. Joan insists on getting the full view of where her latest task leads and God obliges. Joan sees a rapid flash of images that showcase the results of her actions and she quickly blacks out from sensory overload.

Tabletop RPG

Gotterdammerung of Forgotten Realms, called "Karsus's Folly" after the only human who achieved godhood by spellcasting only. He researched and cast the spell borrowing the divine status of an existing deity, but couldn't handle the job the goddess of magic had to do. As a result, the world's magical circuitry began to fall apart so that 12- and 11- level spells don't work anymore. To save what's left Mystril had to turn it off, killing herself and turning Karsus into an "immortal" corpse knowing how much he screwed up everything. And that's before the spell took its full effect.

Video Games

The titular scrolls from The Elder Scrolls are divine artifacts from outside space and time. If a mortal attempts to read them they usually go blind, go insane, or simply die. There's an order of monks who spend their whole life preparing to glimpse an Elder Scroll through study and meditation, knowing that the knowledge they attain will permanently blind them, but also give them glimpses of the distant past or future.