I'm not a great player, but most people would recommend finding your problem balls and taking care of your problems as soon as you can whether it's 8 ball, 9 ball or straight pool. When your plan goes wrong, which happens to everybody, develop a new plan. In the game of 8 ball, which I think is what you're talking about, it isn't always best to go for the runout. Sometimes it is better to let the opponent open up the table.
As far as drills, if you are having problems running balls equal offense should help.
As far as drills, if you are having problems running balls equal offense should help.