The optimal approach to trust?

Trust thought for today - Goldilocks Trust!

Still pondering the question I was asked on what's the optimal approach to trust. Goldilocks trust - not too much that you are constantly taken advantage of. Not too little so that you are permanently suspicious and paralysed. (Trusting even those proven to be untrustworthy can change everything.) What's 'just right'?

Trusting but Vigilant? Vigilance sounds so tiring, but I am meaning to default to trust, but keep a look out in case you are wrong!

Any thoughts?