By what authority do you, or any other catholic, do the same when you make your understanding of Scripture?
The Church! According to the Bible Itself, the Church is the "pillar of truth" (1 Timothy 3:15), not the Bible. Is private interpretation of the Bible condoned in the Bible Itself? No, it is not (2 Peter 1:20). Was individual interpretation of Scripture practiced by the early Christians or the Jews? Again, "NO" (Acts 8:29-35). The assertion that individuals can correctly interpret Scripture is false.
Can there be more than one interpretation of the Bible? No. The word "truth" is used several times in the New Testament. However, the plural version of the word "truth" never appears in Scripture. Therefore, there can only be one Truth.
When it comes to interpreting Scripture, individual non-Catholic Christians claim the same infallibility as the Papacy. If one were to put two persons of the "same" non-Catholic Christian denomination (i.e., two Presybterians, two Lutherans, two Baptists, etc.) in separate rooms with a Bible and a notepad and ask them to write down their "interpretation" of the Bible, passage for passage, shouldn't they then produce the exact same interpretation? If guided by the Holy Spirit as Scripture states, the answer should be "Yes." But would that really happen? History has shown that the answer is "No." Now, in the case of Catholics, the Church which Christ founded and is with forever (Matthew 28:20) interprets the Bible, as guided by the Holy Spirit, (Mark 13:11) for the "sheep" (the faithful). The Church (not individuals) interpret Scripture. In Catholicism, Scripture is there for meditation, prayer and inspiration, not for individual interpretation to formulate doctrine or dogma.