Three different ideals; none are ever fully achieved, but often one of these is regarded as the ideal*.
1. Thinking-led. The normal ideal of 'rationality', Enlightenment, science... now bureaucratic mainstream public discourse.
We think about stuff, decide what to do, and then do it.
Doing it requires 'will power'. We analyse, plan then consciously push our way towards the goal. Future-dominated: life plans, career plans, national plans, salvation plans...
Satisfaction comes from looking-back, from the contemplation of objective, publicly-acknowledged achievement: hard cash, official titles and honours, bricks and mortar, facts and figures...
2. Instinct-led. The idea is to elminate conscious choosing; and instead just to do whatever is spontaneous, natural, immediate. Plans are abandoned...
If hungry: eat; if want something: grab-it; if bored: cease; if tired: rest. If it makes you feel pleasure: do more; if it makes you feel pain: stop...
Live in the moment, here and now; ignore the past, ignore the future, other people are tools for gratification.
The natural is good; short-termism the only sure reality.
3. Intuition. We get an inner feeling that we should do, or not do, this. We become aware of a feeling - not a reason, not an instinct; but coming from the depths of the heart, from the inner self. Un-caused, original, self-generated.
Negative examples: a persistent/ recurrent/ solid knowing that 'I am getting worse'; or that this place is wrong, this job is wrong, I am on the wrong track. This is a bad person.
The knowing may be very general - wrongness - but acknowledgment and attention will make it become more specific (as specific as needed, as specific as possible). The knowing is known not to come-from anywhere external, but to arise in consciousness.
Positive examples: Love. Being drawn to a person, a place; patriotism for something.
The feeling is for-itself, self-justifying, a bottom-line (e.g. to love a person not for use, not for gratification, not to get something - but for himself, herself).
Joy: delight in this/ here/ now - Not for pleasure, but for delight: a slow, strong current; a rising swell of the sea.
This Is Important (although I could not explain why, rationally; and it isn't gratifying me emotionally - here and now).
A knowing that has been trying to be noticed, maybe been in the background unconsciously; a recognition that you have been trying to ignore or over-riding (due to its being unsupported by rationality, or because contradicted by impulse).
Or a sudden knowing, arising in consciousness and with innate conviction: one sees somebody or some-being, of thinks about them - and one knows some-thing: the knowledge is there, a fact.
A solid sense of this being From My True (eternal) Self; instead of the mass of usual stuff - coming from the false/ public/ constructed/ manipulated/ temporary and changing self.
Leave aside, if you can, secondary (second-order) concerns about whether or not some ideal is true and certain, how one knows some-thing is true or certain. Try first (primarily) to understand the different nature of these ideals.
Very few people ever get so far as to understand what exactly it is that they are trying to be certain about. Even fewer try...
...Like the many people who believe 'science' is valdi and certain - but don't know what science is, or what bits of science are supposed to be certain (Facts? Theories? - Which ones? How expressed? Who decides, and why?). But they believe in the need for certainty, they believe with certainty.
They will, for instance commit violence and murder for the belief that "'racism' is evil"; but the word remains undefined, incoherent, fluidly- interpreted - and no attempt is made to solve this. Quite the opposite!
Putting the secondary as primary; they believe in the certainty of... black box abstractions. In practice this reduces simply to certainty in My Opinions; public assertion of My Moral Superiority.