Achievement and success mean different things to different people - we see this in the different ways we all approach our lives. Tremendous sporting success is the lifetime ambition for some, intellectual mastery for others. It may indeed be both of these goals, it may be neither. Our aspirations are limitless, we each are able to pursue whatever ends we desire.
This idea of infinite aspirations is powerful, invoking a feeling of tremendous possibility. This feeling is immediately replaced by an equally powerful sense of anxiety. Infinite options means an impossibly difficult choice, it's hard enough deciding with finite options!
Rest assured, there is a caveat. It comes in the form of a universally-accepted form of existential dread...we all run out of time. This is the most important constraint we face and one of the reasons for our limited capabilities.
Adding to this universal time constraint, we face limits on a more individual level. For one, we are simply not passionate about a huge number of these possible ambitions. Your ability to produce incredible things hinges on consistent, focused time on a chosen endeavour. Overcoming the obstacles which arise will defeat you without this fervent belief in your art/work.
Skill, too, functions as a barrier for many aspirations. You cannot complete work to high levels without building a tremendous amount of ability in a given field (or combination of fields). This means dedicated time spent practicing, failing and learning from these failures. You must assimilate these learning and build momentum to master your craft. There is no substitute for this practical time spent on your craft, it is a necessary and challenging step towards your personal victory.
You are limited also by the way in which you view the world. Unsuitable mental models result in plans untethered from reality and uninformed by the past. Your views reflect the way you are, not the way the world is and you lose opportunities because of it. Being prepared to constantly update and adjust your models with new information equips you better - you will become more in line with reality and respect constraints instead of denying their existence.
"Seek knowledge of the past as an aid to the understanding of the future, which in the course of human things must resemble if it does not reflect it." -Thucydides
Okay, so we have infinite possibilities but necessarily finite capabilities. This is actually a really meaningful, important idea to recognise. You don't have time to pursue every opportunity, only those that are within your capabilities. Understand your intended destination and current location. Between these points lies what Steven Pressfield calls 'The Resistance' in The War of Art.
We are all-too-familiar with this chasm. It stands between our current performance and future potential. Victory versus defeat. The life lived versus unlived. This asymmetry between aspirations and capabilities constrains the way we approach challenges. This is the reason strategy must be employed in the pursuit of achievement.