If you want to be able to play a tune X times through, then try it to see if you can. If you can’t then figure out what the difficult spot is (for me it’s usually the start of a part or a repeat) and work on that until you’ve got it, then try to play X times through again. Break down and isolate the difficult parts and then put them back into the tunes, and work on what’s holding you back from being able to do what you want to do (i.e., don’t work on what you can already do well – that’s playing, not practicing, and you will only improve through practice).
In one of Barry Greene’s books he observes that amateurs practice something until they can play it right; professionals practice until they cannot play it wrong. All my advice is geared towards the later category. When I play a tune in public, I generally want people hearing me to think, “Oh, that’s quite nice. I’d like to hear more.” I want people who I play with to enjoy my playing, and not be thinking “oh, not him again!”