The heart is physically the most vulnerable spot in the body, and emotionally we relate to the heart as being the seat of emotions like grief, vulnerability, insecurity, shame, sadness, betrayal and heartbreak. So to practice Ishvara Pranidhana, we must be willing to be vulnerable to all that God will give us in our life, with the belief that it will be for our highest and best good.
Those two things must be held together or we cannot truly give our whole heart to God. The foundation is faith and firm belief that God will guide us benevolently toward the best outcome – even if we cannot see it in the moment. With that belief we can open the whole heart and give up control and give up attachment to the outcome and just be with the circumstances that surround us. This is where all the niyamas help out and support Ishvara Pranidhana. Practicing contentment, purity, burning self-discipline and self-knowledge , helps us overcome the fear that arises with vulnerability. Ishvara Pranidhana is something to choose each day; choosing to live with the fear that might arise with choosing vulnerability.
We choose the open heart and risk vulnerability because we understand that it is the only way to connect authentically with others. When we allow heartache, betrayal, grief and longing to flow through our heart without resistance, then the result is feeling comfort, forgiveness, peace, contentment, and joy in our relationship to others.
A posture to practice this week for opening the heart to God and accepting courageously the accompanying vulnerability is camel pose. 
The pictures for this blog post comes from here. You will also find a nice explanation of the heart center from a holistic view at this link. And camel pose pix here.
A TED talk about vulnerability and human connection can be found here
