The OP offers the following description of simultaneously holding contradictory positions:

For example, to simultaneously believe and hold that everything is real (in a sense) and nothing is real (in a sense) - and to accept both simultaneously, 100% of the time, as a working model of reality. That everything matters and nothing matters, simultaneously and truthfully.

The OP clarified this in a comment to @DavidBlomstrom:

This isn't multitasking, which suggests switching between different views, nor is it about believing in multiple schools of thought. Its more about believing that a seemingly simple question such as "what is true" or "what is good" or "what matters", can be answered at any given time, from multiple perspectives.

From a philosophy of mind perspective this would be a view that the mind is not a single substance. This contradicts Descartes' conviction. As Edward Feser describes this (page 26)

In knowing for certain that "I think," what I know to exist is precisely a single thinking thing - after all, "I think," not "we think."

Unlike the body which has parts, Descartes' mind does not. However, Feser mentions some evidence from psychological and neurological research suggesting that "Descartes was wrong about the mind's simplicity" such as multiple personality disorders (MPD) and patients with a severed corpus callosum. (page 27)

Such patients are claimed by some researchers to behave as if there were two people living in the same body, each controlling one half of it: for instance, one of the patient's hands will attempt slowly to stack blocks while the other moves in, as if impatiently, to stack them quickly, only to be pushed aside by the first hand.

As a response to these interpretations, Feser writes: (page 27-8)

The reality is that it simply isn't clear that MPD cases (which are extremely rare and difficult to confirm) really are, in the first place, cases of multiple minds existing in one body. Many well-known cases of alleged MPD - such as that of "Sybil," made famous in the film of that title - have been shown to have been exaggerations or even hoaxes. "Sybil" herself has admitted that her "disorder" was more or less her own invention, that she was coaxed into believing that she had multiple personalities by therapists eager to prove that MPD was real, and that under their encouragement and in an emotionally fragile state she had manufactured and acted out various "personalities" to confirm their diagnosis.

All of the examples of indecision seem to be well explained by David Blomstrom as one mind "multi-tasking".

Feser, E. Philosophy of Mind. (2006) Oneworld.

The OP offers the following description of simultaneously holding contradictory positions:

For example, to simultaneously believe and hold that everything is real (in a sense) and nothing is real (in a sense) - and to accept both simultaneously, 100% of the time, as a working model of reality. That everything matters and nothing matters, simultaneously and truthfully.

The OP clarified this in a comment to @DavidBlomstrom:

This isn't multitasking, which suggests switching between different views, nor is it about believing in multiple schools of thought. Its more about believing that a seemingly simple question such as "what is true" or "what is good" or "what matters", can be answered at any given time, from multiple perspectives.

From a philosophy of mind perspective this would be a view that the mind is not a single substance. This contradicts Descartes' conviction. As Edward Feser describes this (page 26)

In knowing for certain that "I think," what I know to exist is precisely a single thinking thing - after all, "I think," not "we think."

Unlike the body which has parts, Descartes' mind does not. However, Feser mentions some evidence from psychological and neurological research suggesting that "Descartes was wrong about the mind's simplicity" such as multiple personality disorders (MPD) and patients with a severed corpus callosum. (page 27)

Such patients are claimed by some researchers to behave as if there were two people living in the same body, each controlling one half of it: for instance, one of the patient's hands will attempt slowly to stack blocks while the other moves in, as if impatiently, to stack them quickly, only to be pushed aside by the first hand. Again, it would appear that what was once a single mind has divided into two.

As a response to these interpretations, Feser writes: (page 27-8)

The reality is that it simply isn't clear that MPD cases (which are extremely rare and difficult to confirm) really are, in the first place, cases of multiple minds existing in one body. Many well-known cases of alleged MPD - such as that of "Sybil," made famous in the film of that title - have been shown to have been exaggerations or even hoaxes. "Sybil" herself has admitted that her "disorder" was more or less her own invention, that she was coaxed into believing that she had multiple personalities by therapists eager to prove that MPD was real, and that under their encouragement and in an emotionally fragile state she had manufactured and acted out various "personalities" to confirm their diagnosis.

All of the examples of indecision seem to be well explained by David Blomstrom as one mind "multi-tasking".

Feser, E. Philosophy of Mind. (2006) Oneworld.