To walk after the spirit a believer must inhibit his mind from revolving endlessly. If it turns too long around one topic, worries or grieves too much over matters, and ponders too intensively to know God's will, it may become unbearable and hamper its normal operation. The mind needs to be kept in a steady and secure state.
Watchman NeeMay the things of this world so lose their power over us that we do not in the slightest wish to be 'worldly'; nay, we even delight in not remaining 'in the world.'
Watchman Nee