The Blessed Buddha once said:
When one attends carefully & rationally, unarisen Sense-Desire does neither
arise, nor later expand.
When one attends carefully & rationally, unarisen Evil-Will does neither arise,
nor later expand.
When one attends carefully & rationally, unarisen Lethargy & Laziness does
neither arise, nor expand.
When one attends carefully & rationally, unarisen Restlessness & Regret does
neither arise, nor expand.
When one attends carefully & rationally, unarisen Doubt & Uncertainty does
neither arise, nor expand.
Furthermore the Awareness link to awakening arise, & is gradually completed by
mental development.
Any unarisen Investigation link to awakening arise, & is gradually completed by
mental development.
Any unarisen Energy link to awakening arise, & is gradually completed by
repeated mental development.
Any unarisen Joy link to awakening arise, & is gradually completed by meditative
mental development.
Any unarisen Tranquillity link to awakening arise, & is gradually completed by
mental development.
Any unarisen Concentration link to awakening arise, & is gradually completed by
mental development.
Any unarisen Equanimity link to awakening arise, & is gradually completed by
mental development.
Source (edited extract):
The Grouped Sayings of the Buddha. Samyutta Nikaya.
Book [V:93-4] section 46: The Links. 35: Careful Attention...

Updated:
09 Nov 2008
http://What-Buddha-Said.net/drops/II/Careful_and_Rational_Attention.htm