"Ye observe days, and months, and times, and years." These were the observances that both Paul and many of the Galatian believers had done in the past when they were children under the law. But now these observances have been "done away" (2 Cor. 3:11-14). They are but shadows of that which was great, that which was to come, the mystery of godliness (1 Tim. 3:16), which Paul preached was in Jesus Christ.
Since the Galatians have taken up again the elements, or rudiments, of the law, from which they were delivered through grace and faith in Christ, he says that he is afraid of them, afraid that he has bestowed his labor, the labor of preaching the pure gospel to them, in vain, verse 11.
In verse 12 Paul encourages them to "be as I am," which intimates that they should be standing in the grace of God (Rom. 5:2) and not in the elements of the law. Paul is only a sinner saved by grace, delivered from the offenses of the law, and made new in Christ; therefore, he can also say "I am as ye are." Their turning back to the law has not injured Paul, but it has injured the cause of Christ and the cause of the preaching of the gospel of Christ. Their witness was overshadowed by the rudiments of the world, and not after Christ (Col. 2:8).
Paul originally came to them with "infirmity" and "temptation." The infirmity is from a word that means "weakness," so this could have been some type of physical ailment that Paul had (many say his eyesight was dim--Gal. 6:11). The temptation was some type of trial that he may have been having as he did his work among the Galatians. Whatever it was, the Galatians knew of it, and they were well with it and even showed him kindness in it and joy in the message that he brought, which was the gospel of the grace of God, verse 13-14, and they received him as an angel, or as they would an angel of God.
In those beginning days of Paul's preaching to them the gospel of Jesus Christ, they loved him so and was so kind and blessed to him that they not only spoke of that kindness to him, but they would have also plucked out their own eyes and given to him (which lends another evidence that his weakness could have been his eyes). This is how much they loved, grasped, and propagated the gospel of Jesus Christ at the first, 15.
But now they seem to be enemies of Paul. Why? It is because they have now turned from the pure grace of God (in their teaching) to the beggarly elements, whereunto they desire to be in bondage (see verse 9). It seems that they have become his enemy because he tells them the truth and will not go with them to the new doctrine of Mr. Law; that is, the law mixed with grace, which is not grace at all (see Rom. 11:6). Law and grace have always been enemies, for the law does not allow for grace; it allows only for mercy. Paul will continue to tell them the truth no matter what they do, because once the message of the gospel has gone away from its true character and principles, the message will continually change to please the ears of hearers; but the truth never changes. John 17:17 -- Sanctify them through thy truth: thy word is truth.