Final answer:
The phrase "much too far out all my life" reveals a deeper emotional and psychological struggle within the speaker, signifying a lifetime of feeling overwhelmed and misunderstood by others.
Step-by-step explanation:
The phrase "much too far out all my life" in the last stanza of Stevie Smith's poem "Not Waving but Drowning" significantly adds to the depth of the work by highlighting a layer of meaning that extends beyond the physical scenario of drowning. It symbolizes emotional and psychological distress, suggesting that the speaker was overwhelmed and struggled with ‘drowning’ in the figurative sense throughout life. This line underscores the central theme of the poem, which deals with the inability of others to recognize or understand someone's internal suffering, and contrasts with the misperception of the speaker's outward behavior as carefree or playful ("always loved larking").