Radak: I did not learn and guard with two hearts; I engaged in Torah for the sake of deed, and with intent for his Avodah, and not to acquire a reputation among people.

Malbim: Above (2), it said "those who guard His Edus, they seek Him with all their hearts." I reached this level.

Radak: I should not err about them. Since He has the ability to give Chachmah and understanding, and He gives - "va'Amalei Oso Ru'ach Elokim b'Chachmah uvi'Svunah", "uv'Lev Kol Chacham Lev Nasati Chachmah" (Shemos 31:3, 6), when He does not give to one who requests it, it is as if He makes him err. This is like "Lamah Sas'enu Hashem mi'Derachecha" (Yeshayah 63:17). If You would remove from us the distraction of Galus, we would go in Your ways, for our hearts desire this. The harsh distractions that weary us in Galus do not allow us. Via leaving us in Galus, it is as if You make us stray from Your ways!

Malbim: Amidst great investigation, sometimes he errs about Mitzvos Hashem and relies on his reasoning and investigation, like Shlomo said "I will increase [wives], and my heart will not veer." There is a difference between Shegi'ah and Shegagah. The former is a mistake in investigation. Shegagah, followed by the prefix Mem, means that via Shegi'ah, he does not do the matter. David requests that this not occur to him.