First and foremost, our selfishness.

The real hindrance to intercessory prayer is, of course, the fact that we live and move in such a narrow circle about ourselves and those nearest us that the Spirit of prayer cannot create in our hearts true zeal for others. The reuslt is that our labors in intercessory prayer often become very circumscribed, and in many cases utterly impossible.

Hallesby, Prayer, loc 1083