I have always thought about this particular verse as it express dual ideas about the Word of God at one go.
Your word is a lamp for my feet,
a light on my path.
This is what I believe the verse is saying:-
Lamp ------- Feet (The Word watches over every step I take in life)
Light ---------Path (The Word gives direction throughout my journey)
The Word of God covers my entire walk in this life. I'm covered!
It is this journey that brings us HAPPINESS
God Bless your journey!