I think it's part of the 3 hearts of entrusting that show up in the Visualization Sutra. This idea was fleshed out by Shan Tao, openly expounded by Honen, and still shows up in the writings of Shin teachers like Shinran & Rennyo. The first heart is the genuine heart and it means honestly looking at oneself, speaking honestly about one's practice, and being earnest in one's efforts to escape samsara via Pure Land birth. Funny enough, I'm finding huge parallels between this concept of the genuine heart and Bhante G's book "Mindfulness in Plain English". The second heart is the profound heart and it means the realization that one is flawed (bonbu nature), that one can't escape samsara by one's own efforts, and a reliance on the 18th vow. The third heart is the heart that dedicates merits to achieving birth in the Pure Land. These 3 hearts are not separate and they come about naturally through the practice.
ShanTao and Honen were pretty adamant that one needed a healthy disdain of the world of suffering in order to genuinely engage in the practice; lamenting those poor beings that didn't want to be born in the Pure Land. Shinran was honest (at least in the Tannisho) in saying that he sometimes he wasn't sure if he really wanted to go there.
The thing is that none of the 3 really recommended leaving the world to hide in the Pure Land for all of eternity. The idea was to attain Pure Land birth and then work to alleviate the suffering of all sentient beings. The assurance of this birth (ojo, anshin, shinjin) was something that could be realized in this lifetime; and (at least in Shin teachings) it's after realizing this assurance that one really feels the gratitude. The main Shin practice then becomes "deep listening" for the workings of infinite compassion in one's life. These are specific instances that one makes a habit of recognizing and feeling grateful for; not really so much just a general sense of gratitude.
As mentioned above, all 3 schools of thought recommended realizing one's bonbu nature in order to cultivate this true reliance on the vow and the settlement of the confidence in one's Pure Land birth. The point of realizing one's bonbu nature is not to engage in any sort of self-hatred; it's to establish that reliance. Once that reliance is established, we realize that any good we perform is through the workings of infinite compassion and not our own calculated, self-interested doing.
At the same time, it's important to realize that we are accepted just as we are. It's the world of the 3-poisons that we wish to cast aside; the suffering. To achieve a Pure Land birth means to embody (ie take on the adornments) of the 37 limbs of enlightenment and work to alleviate the suffering of sentient beings. We don't cast aside our limited selves, so much as realize our limitations and drop the thinking that we have the control to be able to dictate our enlightenment.
Gatha in Praise of Amida Buddha by Master T'an Luan (Jp. Donran) wrote:Immeasurable is the Light of Wisdom (sic: of non-descrimination);
So the Buddha is called 'Immeasurable Light'.
All limited beings are blessed by the Light.
Hence, I bow my head to the Truly Luminant One.
Boundless is the Light-wheel of Deliverance:
So the Buddha is called 'Boundless Light'.
Those touched by the Light are freed of being and non-being.
Hence, I bow my head to the Equal Enlightenment
The Light-cloud is unhindered like open space;
So the Buddha is called 'Unhindered Light'.
All those with hindrances are blessed by the Light.
Hence, I prostrate myself and worship the Inconceivable One.