My doubts become shadows in the sunlight of my determination.

Shadows don't disappear in sunlight. They get shorter and move behind you.

That's a better description of doubt than the line intends. Determination doesn't delete the voice saying you're unqualified; it changes where the voice sits relative to your feet. It still comes along all day. It just stops walking in front of you.

The practical test is simple: did the doubt stop you, or did it just talk while you worked? Only one of those is a problem. Let it narrate. Keep moving.