Re: petere, it's not about Romans, rather the original meaning that provides insight into the pure form of competition. There is a great book called "True Competition" by David Shields that explores this topic and tries to answer the question "How to make competitions more healthy so they don't deteriorate into something that destroys the original spirit of competition".
It's also interesting that in English word "competition" is also used for business, economics, biology, and political sciences. In business, it's clear that competition is a tool to incentivize market players to pursue the highest quality of service at the lowest cost ("show your best"). Again, in monopoly/monopsony, there is no competition – we need other players for that – and no incentive to "show your best".
On Magnus - there's a huge chess subculture, so it's hard to reference any given thing. I might start with this [1]. He's giving every single reason for why he might decline in the future, which I think terrifies him. It's quite unpleasant to imagine that you'll not only never be as strong as you once were, but that you will start to see your strength all so gradually decline, year by year.
So amongst his million preemptive excuses, you also him somewhat rewriting history now claiming his "2 down, 5 to go" comment was "just trolling." He made that comment after his second world championship victory, which was extremely convincing - as it was against the previous generation of players. For some context, no chess world champion has ever won/defended their title more than 6 times. The most dominant champions ever, Lasker/Karpov/Kasparov all won/defended 6 times a piece. Magnus, it seems, will go down with 5.
[1] - https://www.chess.com/news/view/carlsen-on-his-future-person...
This is further emphasized by the fact that the one opponent he was willing to play is a brand new player on the scene who is absurdly insanely good at bullet (1 minute) chess, but has had relatively mixed results in classical (bear in mind he IS a top 10 player), is prone to psychological issues, and is very young with 0 experience at the world level. He somewhat predictably ended up scoring 0.5 points away from last place in the candidates event - and that is who Magnus wanted to "challenge" himself with, like a cat challenging himself with a particularly fast mouse.
---
Also, I was curious about the petere issue, as the Romans in particular took their competition quite competitively. Looking it up, it seems that it means many things such as attack, assail, aim at, etc. [1] But it does not seem to mean to strive, let alone with?
[1] - https://en.wiktionary.org/wiki/peto#Latin