Open arms are also the least protected position a body can take. Anyone who has been left badly knows this, which is why the arms tend to fold on their own.
Welcoming love is not a matter of feeling unafraid first. It is closer to leaving the door on the latch: replying to the message, saying yes to a second coffee, letting someone see the flat before you have tidied it.
Small unguarded acts, carried out while still slightly guarded. That counts. That is how most people manage it.