Confidence in the accuracy or importance of beliefs can be based on strong reason, flimsy fancy, and everything in between. Contemporary people seem to have no particular connection between the strength of their beliefs and sufficient evidence for them. It is not difficult to find a person who has far too little confidence in beliefs for which they have strong evidence nor a person who has far too much confidence in beliefs for which they have insufficient evidence. In fact, you may be an example of both.
If you have too much confidence in your beliefs, you will harm your ability to notice and accept better beliefs. It is dishonest to have strong feelings about weak beliefs. If your observations or your ability to interpret them are highly limited on a given topic, it is dishonest for you to hold strong beliefs about that topic.
Strength of belief, when accurate, comes through living what you believe and finding that the outcomes you expect follow from the causes you predicted they would, in exactly the way you expected. To the extent this occurs across more cases, you should increase the strength of your belief.
In times when it is easy for you to live according to your beliefs, the degree of confidence that you have in them is less important. It is when opposition arises that your confidence matters the most.
Enduring confidence comes through the accumulation of positive outcomes from conscientiously chosen beliefs lived fully. The more evidence you have that your actions align with what you value the most, the more confidence you will have.
You cannot grow in confidence without actually living your beliefs, because you will not gain any evidence for them without putting them into practice. You come to greater confidence through more intentionally identifying and choosing your beliefs, through living them more fully, and through accumulating experiential evidence—evidence both that they are correct in their mapping of cause and effect, and that they yield better outcomes than any alternative beliefs or actions.
Many people are smart enough to know that while living your beliefs can increase your confidence in them, it can also produce counter evidence against them. This is one reason why so few people actually live their beliefs, even if they loudly profess them and tenaciously fight to defend them. It is easy to avoid living what you claim to believe out of fear of the possibility of contradicting them, but you need to understand that there is no benefit to holding potentially false beliefs that is not dwarfed by recognizing them as false. It is better to know you know nothing than it is to think that what you believe is true when you are capable of knowing it is not.