You can come to different conclusions depending on future observations, for example, in which case further reflection would not move your level of certainty, the belief would be stable, and yet you'd remain uncertain. For example, consider your belief about the outcome of a future coin toss: this belief is stable under reflection, but doesn't claim certainty.

Generally, there are many ways in which you can (or should) make decisions or come to conclusions, your whole decision problem, all heuristics that make up your mind, can have a hand in deciding how any given detail of your mind should be.

(Also, being certain for the reason that you don't expect to change your mind sounds like a bad idea, this could license arbitrary beliefs, since the future process of potentially changing your mind that you're thinking about could be making the same calculation, locking in into a belief with no justification other than itself. This doesn't obviously work this way only because you retain other, healthy reasons for making conclusions, so this particular wrong ritual washes out.)