It depends on what you mean by ‘New Age’ or ‘Spiritualism.’ If we are talking about stuff like A course in Miracles, Eckhart Tolle, Chicken Soup for the Soul, Niel Diamond Walshe, ‘The Secret’ and things like that, generally for Christian prayer and spiritual life they are worthless.
Unfortunately people sometimes also lump perfectly orthodox Christian mystics like John of Cross, Meister Eckhart, Teresa of Avila or others in with the New Age and spiritualism. Christians should turn to great saints, doctors, and mystics in the Christian faith rather than New Age forms of spirituality. The Christian deposit of faith includes many different forms of spirituality for many different kinds of people in different stations of life. It is up to each Christian to decide which devotions or prayer methods or spiritual paths are appropriate to them, but all should led to God through Jesus Christ.