What should you not abandon?
R. Yonah: My Torah [and it will guard you].
What is the meaning of "Ehaveha"?
Rashi: Love it (Chachmah).
R. Yonah: Do (serve Hashem) amidst love. Therefore it says "v'Sitzreka", which is a higher level than Shemirah. Shemirah of money or Kelim - one leaves them [in a secure place], and a Shomer Sachar guarding a donkey or ox grazes it, lest it weaken. Netzirah includes improving the matter, and accepting the Tikun that it is proper to receive - "Notzer Te'enah Yochal Piryah" (27:18), "Ki Shamru Imrasecha u'Vrisecha Yintzoru" (Devarim 33:9).
Malbim: Love is a greater level than not abandoning. Sometimes one does not abandon something, even if he does not love it, if he benefits from it. Therefore the verse adds that you will love it and your Nefesh will cling to it, due to the good in it. This is greater than what is pleasant and beneficial. Via this, it will guard you. When you increase love, "v'Sitzreka", which is a much higher level than Shemirah.
