When I used to surf we had a saying (and I am sure it is still out there but I don't hear it any more) "Go big or go home" If you were not pushing yourself to go after bigger waves or bigger tricks there was no point in being in the water. If you were not there to be a better surfer every time you got in the water why get in the water. The scale of big differed from one person to the next, the novice was going big paddling in to a four foot wave or even getting to his feet consistently, more advanced surfers might be going big at teen feet or making a good bottom turn.
If we are to grow we must be ambitious. Setting our sights on things that are near at hand and trying to achieve those will get earn us successes but they will be small ones. We will only grow a little, gain a small amount of confidence and not cover much ground towards our larger goals. On the other hand if we push to far the risk of not meeting our expectation rises, our chance for disappointing our selves increases as does our potential to give up. So what we need is realistic ambition.
The key to realistic ambition is to know yourself. Know what you can do, know what you can probably do and know what is beyond you. The target area, once confidence is built, is the probably do. We must however be honest with ourselves about which is which and not find ourselves trying to do too much to impress others or to little because we are scared. Ego is better served through successes for ourselves and fear should be faced unless it leads to injury or death.