We need to be guided in our interpretation of 2 Peter 1:10 not only by the context provided us by Peter, but also by the context provided us by all the other inspired authors of the Bible.
Thomas Constable, in his notes which accompany the NET Bible at bible.org, quotes Richard Bauckham (Jude, 2 Peter. Word Biblical Commentary 50. Waco, Tex.: Word, 1983) as follows:
“This passage [viz., 2 Peter 1:10] does not mean that moral progress provides the Christian with a subjective assurance of his election (the sense it was given by Luther and Calvin, and especially in seventeenth-century Calvinism) . . .”.
In other words, what does provide the Christian with a subjective assurance of his or her election are primarily the promises of God, and only secondarily (if that) the occasional naval gazing about our standing before God, which is unchangeable, in light of our state before God, which is highly changeable. Our faith, firm belief, and trust in the promises of God regarding our salvation are so much more important than the feelings we get by constantly monitoring our progress in sanctification.
Do we need periodically to check our progress (or as Peter puts it, "confirm [our] calling and election")? Yes. That progress check, however, is only part of the process of sanctification. Another important part--and here is where the "both/and" kind of thinking is helpful--is to reassure our hearts by such things as the following (not an exhaustive list, by any means):
the trustworthiness of God to bring to completion what he has started in our lives. "For I am confident of this very thing, that He who began a good work in you will perfect it until the day of Christ Jesus" (Philippians 1:6 NAS); and "Now to Him who is able to keep you from stumbling, and to make you stand in the presence of His glory blameless with great joy . . . (Jude, v.24).
the love and power of God to keep his sheep safely in the hollow of his hand. Jesus said, "'My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they will never perish; and no one will snatch them out of My hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father's hand'" (John 10:27-29 NASB Updated.)
the centrality of faith in our salvation and in our progress in sanctification. Faith is not just knowing; it is knowing that we know. Faith depends not primarily on logic, reason, and infallible proofs; rather, faith believes in and banks on God's promises. When we truly believe in our hearts what God wants and requires us to believe in order to be saved, then we are surely on the road of faith and on the road to faith. As John said in his first letter: "These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life" (5:13 NASB Updated).
the relative unimportance of knowing who is (or will be) saved and who is not (or will not be) saved. As Paul tells us very clearly: "Nevertheless, the firm foundation of God stands, having this seal, 'the Lord knows those who are His,' and, Everyone who names the name of the Lord is to abstain from wickedness" (2 Timothy 2:19 NASB Updated).
Combining at least the last two bullet points, Christians are both saved by faith and are then to walk by faith and not by sight. An inordinate concern about who is one of the elect/saved or who is not one of the elect/saved is an exercise in futility. Only God "knows those who are His." Our primary task is to "confirm [our] calling and election" by applying ourselves diligently to the formation of such qualities within us as moral excellence, knowledge, self-control, perseverance, godliness, brotherly kindness, and love (2 Peter 1:5-7). That is the positive side of things.
On the negative side of things, we are "to abstain from wickedness." In other words, don't concern yourself so much with the other guy's spiritual standing before God, but take heed to your own spiritual state before God, which requires frequent repentance, confession, and cleansing (1 John 1:8-10).
In conclusion, there is no dichotomy between God's unconditional election of the elect and the confirmation of our calling and election. It's not a matter of either/or, but both/and. To insist dogmatically that there is a dichotomy when there is none belies, perhaps, a desire to be right at all cost and not a desire to find common ground and then leave the rest to God, who alone and ultimately has all the answers. As Isaiah said in 55:8-9, where the word My refers to the LORD's thoughts and ways,
"'For My thoughts are not your thoughts, Nor are your ways My ways,' declares the LORD. 'For as the heavens are higher than the earth, So are My ways higher than your ways And My thought than your thoughts.'"
In light of God's omniscience and infinite wisdom, a little humility on our part goes a long, long way, particularly when we are at odds with our brothers and sisters in Christ and refuse to see the merits of their interpretations, perspectives, and reasoning.