When to use your heart or your brain?

First before knowing the answer to this question, you should first get a clear picture of what heart orientated actually means. When you say that you are actually following your heart, it rhetorically means that you deliberately allowed emotions to take over your discretions or judgments. Even emotions are triggered by the brains, though; the real mechanism behind this is unknown. So, most of the times when emotions come into play, we tend to make the wrong decisions.
Intuition is totally a different thing.It is actually the subconscious part of brain trying to reach out, to be heard over your conscious mind, and it is mostly driven by belief and faith.So, in making very important decisions, an interaction between the subconscious and the conscious mind is important(both are in the brain) and henceforth, the compability of the two is unquestionable.
Then 'how about following your heart’? It is strictly not advisable to use this, but in some circumstances where you are required to speak the truth or to give out a value judgment truthfully, then this may become an important aspect as well.