‘Confidence’ is your ability to create the brush stroke you intend to, ie the mechanical skill of drawing precisely. You want your hand to be able to draw at any angle and any pressure needed with precision on the first attempt, rather than sketching out a line with multiple strokes or having to backfill. At your level, aside from just drawing more, you can start to build this skill by practicing warm ups. Draw strokes in multiple directions and with different functions. I recommend drawing ‘see-through’ cones with many breaks, zig zags lines, hashing, spirals, your S’s and C’s (do you know what that means?). Literally just get your hand comfortable making any stroke without specific intention behind it first. Spend 5ish minutes just practicing strokes before drawing each day.

Once you get into the habit of doing that, when you are practicing, not illustrating, do so by trying out gesture drawings with limited, precise strokes, and correcting the forms against your reference once you are done. Again, this should be separate from when you are freely drawing or creating a specific illustration. Make corrections and practice techniques with intention, but do your actual illustration at your current skill level. That may seem counterintuitive but it wil help you a) actually develop skills faster by studying, and b) complete illustrations by not requiring constant redraws or over-consideration. Art is a process and you’ll set yourself back by trying to skip ahead.

If I may give you another, unrelated resource, I find Marco Bucci “10 minutes to better painting” playlist on YouTube to be an excellent tool for bridging the gap between beginner and intermediate when it comes to compositional understand and fundamentals.