An additional strength as a character trait
Enough of these factors to get the desired result
A known input to results ratio
"Until one is committed, there is hesitancy, the chance to draw back, always ineffectiveness, concerning all acts of initiative (and creation)...the moment one definitely commits oneself, then Providence moves too. All sorts of things occur to help one that would never otherwise have occurred. A whole stream of events issues from the decision, raising in one's favour all manner of unforeseen incidents and meetings and material assistance which no man could have dreamed would have come his way." - W.H. Murray
If there is uncertainty one hesitates, proceeds in an "off and on" mode, or never starts, as there is no proper impetus or way to go.
However, once one has sufficient certainty what the right way is and to know what the benefits are, one will be sufficiently motivated to move forward. That is what humans do, assuming sufficient knowledge to eliminate the barriers (read Motivation).
The use of the word "sufficient" means that we just need enough information and enough clarity to move forward, so we don't waste any efforts. It is consistent with the 80/20 principle (Live8020.com) of doing only high payoff items and not doing low payoff items. To understand something we need to have enough "dots" of information AND to have the dots connected. (Dots by themselves, aka knowledge, is not sufficient to get the results we want. This is also an effectiveness/efficiency/power principle: The Law Of Enough Dots.)
AN ADDITIONAL STRENGTH AS A CHARACTER TRAIT
"Certainty" is also a character strength, which is also a way of being able to live a more fruitful, less cautious life. So you should know that one and acquire it, using the principle of sufficient certainty.
ENOUGH OF THESE FACTORS TO GET THE DESIRED RESULTS
The word "sufficient", again, means "enough", but just enough to get the results we want.
Part of that "sufficient certainty" is
1. Having clarity, with sufficient specifics
3. Practicing enough so expert enough
4. Completion to a great enough level to have certainty
A KNOWN INPUT TO RESULTS RATIO
Some results and circumstances have a low or zero level of certainty. If one is engaged in too many of those, then the uncertainty becomes contagious to other parts of your life and your mood and self-talk. There must be sufficient balance overall so that you feel enough certainty about getting "enough".
Identifying those things you can do with certainty (or high certainty) is a worthwhile activity, so that you can put those into effect when you need more certainty.
A psychological exercise that works to change one's viewpoint is the simple exercise of touching and/or having.
If you touch the bark on a tree and describe the details, feelings, textures, etc., it actually adds to your certainty as that is "certainly" a known (the bark on the tree).
Doing the exercise of identifying "what you could have" or "what you figuratively own"actually fills up the emotional tank, amazingly enough. Saying
"I own the sun, it will come up tomorrow"
"I can have that big house over there. I have the blue sky, the fresh air, food..."
So, when should you say those things? Certainly at least when you are feeling uncertain, but I don't believe it is good to wait until you are so far out of harmony and balance. A daily dose of "haves" in the above form or, better yet, gratitude exercises.
While exercise does not have an exact ratio, there is a presumed benefit that is a great one, such that we shouldn't risk not doing it. Exercise adds certainty, plus it adds derivative certainties, such as feeling stronger (and therefore more certain) and feeling more confident that you'll follow through on things.
A REALISTIC ASSESSMENT OF ONESELF
When you have a realistic assessment of your capabilities, your brain will naturally balance off what you do, in order to produce certainty, as it has a good idea of what you can do that will work to produce results.
So many people think they should be "better looking" (which, after a point, is not possible), should be smarter (tough to change that much), should be more popular and much more interesting (one can do something about those, but with some uncertainty, but expecting one to measure up to a person quite a bit above one makes no sense), should be less sensitive (possible to work on, but not as a "should", and the like. These are killers of confidence, as they set up failure after failure after failure, which are not really necessary. Accepting oneself for who one is, at the various levels one performs in various areas, is a key to having certainty (and happiness!).
WATCH WHAT YOU SAY!
ESTABLISH CERTAIN TRUTHS AND EMOTIONAL VULNERABILITY DROPS DRAMATICALLY!
If you have established (by going throught the process of doing so) that you are competent and capable of handling life, you are not threatened by nor vulnerable to the criticism of you by others.
If you have established that you are "worthy" (or not unworthy), then you are not threatened by making mistakes. Or if you know you will be all right even if you make mistakes, you need not be so wary of making mistakes - and your fear and anxiety levels will plummet.
The side effect of establishing what is true for certain is that you will no longer need to "be on the lookout" for supposed threats in the area. Your anxiety level will be so low that you will feel calm virtually all the time!