MCTB The Five Spiritual Faculties
The Five Spiritual Faculties are said to be like a cart with four wheels and a driver. If any of the four wheels is too small or wobbly or not in balance with the others, then the going on the spiritual road will be rough. If the driver is not paying attention then there will also be problems. The four wheels symbolize faith, wisdom, energy and concentration. The driver symbolizes mindfulness.
This is really a useful little teaching and quite a fine list. The trick is that faith and wisdom must both be made strong and kept in balance, as must energy and concentration. Mindfulness may always be increased, so for this one the sky is the limit, but don't be too obsessive about it.
This sounds really simple and perhaps obvious, but there is quite a lot here, and on the spiritual path it is worth checking up on ourselves regularly and asking if the first four are all strong and in balance and if we might be just a bit more mindful.