Do not confuse your highest previous effort with your highest possible effort.

Your best effort so far was made under particular conditions, with the knowledge and preparation you had at the time. It is a data point rather than a boundary. People routinely mistake it for a ceiling, and the mistake becomes self confirming, because you stop attempting anything beyond it and so never generate evidence to the contrary.

Pick something where you believe you have hit your limit and set up a fair test of it, with better preparation than last time. You may find the limit was real. More often it turns out to have been a description of one particular attempt.