Well, this is what the guided meditations are about: learning how to transform negative thoughts into wise ones. With aversion we usually use different types of Compassion/Lovingkindness types of reflections to bend negative ones into wise ones. With sense desire, thoughts about the future, we use Death reflection to bend negative thoughts into wise ones. With worry, fear and doubt, we usually use confidence inspiring objects to bend negative thoughts into wise ones.
Formally we can go much more in depth. Informally, usually a short reflection is very helpful for reflection on the Dhamma. This is where reflection on the Dhamma is extremely beneficial in normal life informally. If you have short reflections that you do at the beginning of the sitting, these are very helpful to get a deeper groove in the mind. If you have memorized any of the Suttas of teachings of the Buddha, these form a deeper groove in the mind.
So formally we may go much more in depth and analyze that particular theme. However, in our normal life we usually don't have the amount of time to go into long reflections, so this is where short forms are very helpful. We can bring up one line and often it actually carries the power of our deeper reflections at that time.
Many of the assistants here have seen that the memorization of the various Suttas has helped them in their normal life. When they see they're getting lost in a particular worldly dhamma or hindrance, sometimes one line of that Sutta comes up and helps them at that time, helping to bend unwise thoughts into wise ones. This is the power of memorizing the Dhamma. And this is the power of having short reflections at the beginning of each sitting. Dedication of intention, short reflection of the five reflections, the Buddha, Dhamma, Sangha reflections when you do the bowing. Sometimes they can be long and sometimes they can be short. But because you've done it in depth, when you bring up one sentence it often has the power of all the expanded reflections that you have done.
So formally and informally: Informally it's more the short forms that usually come up to help one. Formally, we can go into more depth. In order to know what type of reflection to use at what particular time, we have to actually have the power of awareness to aid us in our normal life, to actually know what hindrance we are getting lost in, what eight worldly condition we are getting attached to, so that we can bring up the appropriate reflections to bend unwise energies into wise ones. In order to know what reflection, it helps to have some practice in retreats in the different types of reflections and notice how they affect the mind. By observing how it affects the mind, what results from arise from reflecting in certain ways, we then become more skillful in using the types of reflections informally in our normal life.