"So we are always confident; even though we know that while we are at home in the body we are away from the Lord – for we walk by faith, not by sight" (2 Corinthians 5:6-7 NRSV).
The document we know as Second Corinthians is actually composed of bits and pieces of a number of different letters Paul wrote to the church in Corinth in the course of their stormy relationship. After Paul founded the group and moved on to Ephesus, they fell under the sway of other teachers who understood Jesus differently, causing Paul to return and then leave again, deeply offended by something (we don't know what) that happened while he was there. The church and the apostle eventually resolved their differences, but with all the emotion involved, it's difficult to find a clear line through the letter.
In Chapter 5 Paul is writing about the challenge of containing a new Christ Awareness within the frustrating limitations of a human body and human life. This "earthly tent" he finds a poor substitute for the "house not made by hands, eternal in the heavens" that is our true home (2 Corinthians 5:1). And yet we know that this is part of a divine plan, and that God as the Holy Spirit is always present to remind us, reassure us and encourage us forward.
"So we are always confident," Paul affirms in the passage you've asked about, "for we walk by faith and not by sight." Our five senses report on a limited life experience of duality and suffering. If we “walk” according to the information from our senses, we would be in constant despair. It is the faith that “sees” the bigger picture – the spiritual Allness in which everything rests – that we can trust as a guide through this dualistic experience.