Knowing my audience, especially those of you on Tumblr, you probably don't see yourself as a bold person. In fact, you probably see yourself in the opposite light. Certainly in the safety of your keyboard you can manage bold words, but put you in a public setting and you blend into the background. So if I talk to you about spiritual boldness you probably would not be able to relate. It's because we have the wrong idea of boldness.
Even the most daring and bold person you can think of has a whole attic of unspoken insecurities. Most likely they act as bold as they do to compensate for those insecurities, but that is not how spiritual boldness works. In fact, spiritual boldness has nothing to do with your confidence or insecurities and everything to do with belief and faith in Jesus Christ. All Jesus needs from you is to believe his promises apply to you and then faith to act on them. With these two things in place Jesus is able to accomplish great things through anyone, despite their shortcomings. Consider David.
David had never fought against a man before facing the seasoned warrior, Goliath. His experience was limited to protecting the family's flock of sheep from various predators. But David took the experience and knowledge he had gained about Yahweh and translated it to this situation with Goliath. His thinking was simple: If Yahweh makes it possible to protect these meager sheep he will also make it possible to protect Israel:
How could Yahweh not respond to such a bold trust? Jesus told us time and again to have this same attitude when serving him. Ask whatever you need, is what he said to us. Ask, seek, knock are his instructions. Boldness and determination were the subjects of his parables. Read through the gospels again and look for it. You will be amazed how clear it is.
The Lord doesn't need anything you have to offer him so your spiritual boldness does not depend or your ability or inability. What he needs are more hearts like David; people who know and believe the promises and who have the faith to act on them. Boldness does not depend on who you are but on your willingness to act on who Jesus is. It is not "I think I can" that moves mountains but "I know he wills it". Step out in the boldness of the promises; believe and act on it.