Often Satan injects pride into the believer's spirit, evoking in him an attitude of self-importance and of self-conceit. He causes him to esteem himself a very outstanding person, one who is indispensable in God's work. Such a spirit constitutes one of the major reasons for the fall of believers.
Watchman NeeTo 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 Nee