Hey @Dezza, you’ve already gotten plenty of good advice (and Boardman’s comment is gold), but I’ll add my take on the issue which is quite simple: every metric only serves to inform our perception. So the numbers and the data are extremely useful when it comes to cultivating an understanding of what going all-out feels like, what all-day pace feels like, what a hard but repeatable couple-minute effort feels like and what it feels like when that same couple of minutes is too hard to readily bounce back from.
And, of course, the data is extremely useful when structuring workouts and eking the most from your training as opposed to flying blind until you crack or end up missing the intent of a specific type of workout aimed at a specific performance adaptation; super useful when tracking improvement (or decreases) in fitness too since these objective measures are the very things that allow us to manage our training in measurable, reliable ways.
But allowing the numbers to govern your effort in a race is tricky stuff. Sometimes it can be the difference between pacing effectively and overdoing it early on, it can tell you whether certain scenarios are realistic or out of the question, and it can help you gauge when to eat based on energy expenditure in longer events, things like that.
But all of these have to be weighed against how you feel regardless of what the numbers say, because sometimes you just don’t have it, sometimes you’re verging on breaking down barriers and ‘leveling up’, and in both cases, allowing the numbers to be the only and final word can be counterproductive.
By all means, train by the numbers, maybe even race by them in some instances, but always be building your performance self-knowledge and strengthening the link between what the metrics tell you and how you feel, what you can do regardless of what the data says.