Faith & Instincts

For those who don't know me very well...which would be most of the people reading this...I can be quite random.

I am a person who must know "Why." Why? I just am. God made me that way. I need the elaboration, justification. I need logic. Reasoning.

The questions lately on my mind are: When do we go with our heart over our head? When do we keep doing in faith, or let it all go in instinct?

Even I don't know if I am making sense. Supposedly, one should always keep trying. Keep working, keep the faith. Supposedly, if things are meant to happen, they will happen. If you build it, they will come. At what point do we invest faith in DOING SOMETHING ELSE?