Don't worry about your doubts. Nav is probably the most challenging part of learning to fly. My first couple of Navexes didn't go fantastically well and I remember feeling disheartened (especially when I misidentified my 2nd turning point and ended up 5 miles away from where I was supposed to be. Oops). But that's normal. I quickly got the hang of it and started really enjoying it!
Practice by planning out routes at home. If you have a flight simulator maybe try planning and flying a route. I did that and it helped me on the regular occasions when the Wx was rubbish and I couldn't fly.
Hang in there, it'll eventually become 2nd nature! Good luck.