In his "Preface" to Lyrical Ballads, Wordsworth states: 

I have said that poetry is the spontaneous overflow of powerful feelings: it takes its origin from emotion recollected in tranquility: the emotion is contemplated till by a species of reaction the tranquility gradually disappears, and an emotion, kindred to that which was before the subject of contemplation, is gradually produced, and does itself actually exist in the mind. 

This sums up Wordsworth's function of poetry and echoes the sentiments in the statement from his "Ode: Intimations of Immortality from Recollections of Early Childhood." Nothing can bring back past experiences. Rather than grieve, the poetic goal is to dwell on what is left behind: "soothing thoughts," reflections, and recollections that will fill the "philosophic mind." 

This is a common synthesis in Wordsworth's themes and method of poetic creation: experience, reflection = poetic production in thought and words. This synthesis is a kind of "aufheben" to borrow a word from Hegel wherein the reflection takes over for (and thus abolishes) the experience, thus standing in for it. The same occurs with poetic production; the creation (imagination) takes over for the reflection. This synthetic process involves a "holding up" of the experience (a remembering and therefore not a complete abolishing) but also transcending of the experience into reflection and production. The experience becomes reflection; the reflection becomes "soothing thoughts" and/or poetry. 

Here are some examples of this (past) outer experience, followed by present (and hopefully future) inner reflection. In "I wandered lonely as a cloud," the last stanza encapsulates this idea: 

For oft, when on my couch I lie

In vacant or in pensive mood, 

They flash upon that inward eye

Which is the bliss of solitude;

And then my heart with pleasure fills, 

And dances with the daffodils. 

The outer experience becomes a reflection (mental) - a "flash upon that inward eye." 

In the epigraph of "Ode: Intimations of Immortality from Recollections of Early Childhood," Wordsworth writes: 

The Child is Father of the Man; 

And I could wish my days to be 

Bound each to each by natural piety. 

This is taken from his poem "My heart leaps up." We are children before men. Therefore I, as a child, exist before I exist as a man. The child, linearly, exists before the man. Wordsworth wants his days as a Man bound to his days as a child: his present to his past. Poetic reflection is to be bound to past experience: a synthesis (binding) of the two. Likewise, this implies a bond between past and present (and/or future). 

We should also look at The Prelude, often described as Wordsworth's greatest achievement, as it is a justification of/about poetry (and autobiographical in scope). In creating poetry, Wordsworth reflects/recollects. There is a real sense of "going back" in order to "go forward" and create. At the beginning of The Prelude, the speaker goes back to his childhood. The Prelude goes through Wordsworth's ("the speaker's/poet's) life, from dealing with uncertainty about being a poet, his mother's death, to college, to support and then disillusionment with the French Revolution. 

In Book 12, Wordsworth again "goes back" to youthful experiences. The Prelude, Book 1, begins with "O there is blessing in this gentle breeze," and line 10 of Book 12, "ye breezes and soft airs" returns to a connection with nature and the past. The breeze of the past is similar to the breeze of the present and at the end of Book 12, he shows this connection: 

In a strong wind, some working of the spirit,

Some inward agitations, thence are brought, 

Some outer experience (the breeze, wind) stirs an inward (mental) thought. And this mental thought ("what remains behind") provides the "strength" to get through human suffering; this strength (from the inward thought or the "strong wind" itself) also fuels the imagination of poetic creation.

Recollection and reflection allow the poet to "go back" in order to "go forward" with the strength to deal with things and/or the strength to create. When the recollection is not enough, something as simple yet as powerful as a breeze or another gaze at a flower helps to bond the connections: outer experience/inner reflection and past/present.