John Newton writes a sketch of the believer’s temper. The entire letter is worthy of your consideration but I though this particularly helpful:
Satan will not often tempt a believer to gross crimes—our greatest snares and sorest conflicts are usually found in things lawful in themselves—but hurtful to us by their abuse, engrossing too much of our time, or of our hearts, or somehow indisposing us for communion with the Lord. The Christian will be jealous of anything which might entangle his affections, dampen his zeal, or straiten him in his opportunities of serving his Savior.
What are areas in your life that are “lawful in themselves” but “hurtful by their abuse”?
For me I think certain entertainments like television and video games are the obvious ones. The less obvious ones are spending an inordinate amount of time reading Christian books to the neglect of Scripture and prayer. Surfing the internet and blogging—even if with an intention of doing it for the glory of God—can “engross too much of my time”.
This letter is very helpful, you can read the entire thing here.