Wouldn't worry to much, I did my CPLs last year and must admit at times I did not think I had it in me. Nav was the one exam I did fail but went back a managed to get a reasonable score.
I never really studied at school and never went to Uni and as such had no study technique or really any idea where to start. What I did learn was that when something was really just making no sense at all, take a brake. Go and do something else, if you just keep pulling out hairs it gets you no where. You can read the same thing over and over again and will just keep making the same mistakes, come back with a fresh set of eyes.
Also I found studying at the pub works really well, not great for the more difficult bits but when just reading things nothing better than a pint to wash it down...