How Do I Know...?
The question of certainty is one that often enters into discernment, and especially when we speak of vocational discernment. People want to know where they are headed, and sometimes ask God to show them for sure where His will lies.
It's interesting that people do not require themselves to be certain about remaining where they are, but they ask God for certainty as they take a step. Life often requires us to take risks; that is how we learn. And we learn about our vocation by taking risks - some people risk praying and asking God what He wants for them and their future.
Others are daring enough to go and visit a convent or a community, and still others are daring enough to take a chance and enter seminary or religious formation, but the desire for certainty is not one that is healthy, and can lead us to closure and living "in a rut."