You can’t choose to believe. Beliefs are assertions that you realise you hold. They are not premises you select and opt to support.
Holding beliefs is an entirely passive state-of-being affected by trust and experience. For example, if someone holding a box tells you that there is a ball inside it you will naturally believe them if they are trustworthy. On the other hand, you may not believe them if they are not trustworthy or have a reason to lie to you. You don’t actively choose one way or the other; it’s based on your perception of the person and environment. When they open the box and reveal that it is actually empty, you will now reasonably believe that they were lying. You can’t actively choose to believe they there were telling the truth. If they claim that the ball dissappeared and you are particularly gullible, they may convince you that there was in a ball in the box prior to them opening it (and that this ball somehow mysteriously disappeared). You may even stubbornly assert this to yourself and others because you hold the person in high esteem and can’t accept that they would have lied to you. If they are likeable but not particularly convincing, you may not really believe that there was ever a ball in the box, but you may still act as if there was so as not to offend them.
Often as people age, others may tell them that they have become “set in their ways” or “set in their beliefs”. You can choose to ignore evidence that questions your beliefs (in order that you can continue believing as you do). If you cannot ignore such evidence your beliefs will inevitably change, but you can continually try to convince yourself otherwise, or you can choose to act as if you still believe as fervently as you once did. You may not even choose to act in that way; you may be subconsciously dependent on that belief (and unable to accept evidence to the contrary). I think it’s unreasonable to actively ignore evidence and I think it’s disingenuous to act as if you believe something when you do not truly believe it. A popular argument is that some beliefs provide you with utility (usually “a sense of comfort”). This utility is a reward for you to keep your ears covered and your eyes closed, and I think it’s self-serving and hollow to knowingly accept such a bribe.
It can take great strength of character to open yourself to other opinions and new information, and to resist ingrained ideologies and social pressures. I personally feel that it’s exceedingly important to maintain an attitude of frequent and reasonable reassessment of your beliefs. To determine what you believe is to realise who you are.