Supposedly the Buddha said, the good things, try to do them, the bad things, don't do them. The problem, of course, is to know for yourself what action is good or bad, or as the new spiritual movement tends to say, what action leads you in the right direction on the spiritual path.
The not so useful stuff is growing like weed in your mind. It feels good when you do it, but you know that it doesn't help your spiritual advances if you persist. Moreover, with every additional step you take on your please journey, the clean-up process will get harder.
The good news, our mind is incredibly flexible. Tracks that have been formed can be written over. We can literally re-wire our brain. When you tackle the weed in your garden for the first time, the process appears daunting. However, as you dump loads of mulch on the existing groves, the picture soon gets much brighter. Keep the faith and your hard labor will pay off.