Recently, I came across a similar idea expressed in different works. The idea is simple yet powerful as a practice. It is this:

Dreams are mere illusions. The waking state is similar.

The last stanza of the famous Lakshmi-Nrisimha pancharatna stotra is a prayer eulogizing the Lord in His form as Nrisimha (Man-Lion) along with His consort, Lakshmi. The common refrain of the entire composition is

'O! bee called the mind, why do you uselessly wander in the essence less wasted desert land called the Samsara? Partake with reverence the honey in the lotus feet of Lord Lakshmi Nrisimha.'

My favorite line in this prayer is the idea expressed at the beginning of this post

tava hitamekaM vachanaM vakShye shruNu sukhakAmo yadi satatam

svapne dRRiShTaM sakalaM hi mRRiShA jAgrati cha smara tadvaditi

It means:

If you really desire permanent happiness, I will give you some advice. Heed to it. All that we see and experience in the dream state is not real. Please remember that whatever you see and experience in the waking state is also not real.

{A rendition of the full shloka in Youtube can be found here. The pdf can be found elsewhere at Prapatti and Sanskrit Documents. Both these sites have wonderful repository of shloka-s and vedantic texts, including this one, in devanAgari, roman, mp3 formats.}

The Panchadashi of Sri Vidyaranya gives us similar instructions.

'He who see the world like a dream of a magic, of nature of unimaginable formations, seeming and disappearing – how can he have any attachment in it?'

'After directly seeing his own dream and seeing his own waking state, he must without remissness think about them both, every day, again and again.'

'Contemplating for long the similarity between them (the waking and dream states) in all aspects and giving up the sense of reality in the waking state, he will not have any attachment for it as before.'

This teaching is essentially an upanishad-ic one. The famous mANDUkya upaniShad with the kArikA-s of gauDapAdAcharya uses the analysis of the three states of experience (waking, dream and deep sleep) to negate the illusory world and teach the truth of the non-dual reality. vaitathya prakaraNam, the second chapter, especially contains specific inputs on using the dreams to negate the world.

The various experiences of the dream are only fancies of the mind. They are merely imagined by the mind and have no external reality apart from the mind. The inappropriateness of space and time in dreams gives us the clue. More over, they cease to exist on waking up. In the same way the varied experiences of the waking state are grasped by the mind only. In reality they too have no existence.

(The Mandukya Karika by Swami Gabhirananda of Sri Ramakrishna Math)

There are wonderful explanations and notes on the mANDUkya upaniShad elsewhere in this website by Swami Sadatmananda and Dennis Waite.