One of the best pieces of advice from a QFI:
"Next time you have a sh*t take your radio aids map with you"
Quite seriously we were taught a process called the 'dry swim'. This means going though your next navex, step by step, in your head. Go through all your calculations until the steps become automatic and natural. When you have got it all buttoned up you will get airborne with more spare capacity.
I got lost several times during basic flying training. Once at low level, once at high level and once at night. I even got my QFI lost!
Each time I went back to my room and re worked my calculations. On one occasion it was a simple matter of putting the wind dot on my Dalton Computer in the wrong place.
Even if it means canceling a weekend and sitting in your room for a couple of days practicing it really is worth it. My experience was that there were few naturally gifted military pilots. The ones who got through were grafters - and they usually went round posing that they didn't need to do the work.
There were definitely guys who were chopped because they thought the could 'wing it' on ability.
Best of luck and stick at it.