As things change imperceptibly it can often require an event or passing comment to realise the difference.
This week I replaced the gear cable on my Brompton S2L as I had noticed a pronounced kink in the outer when the bicycle was folded. What I hadn't appreciated was the effort required in flicking the gear selector lever, that is until I rode the bike once the cable was replaced. After two and half years of constant use I guess it was about time the cable was replaced and, as it turned out, the job was straightforward albeit a little fiddly.
Another trigger occurred during a recent cycle sportive when I received a comment that I had powered up a reasonably steep and long climb seemingly effortlessly whilst still on the big ring and to the dismay of several other cyclists struggling up the climb on their granny rings. It genuinely hadn't occurred to me that I was doing it, but then I remembered that four years earlier I was the one struggling up a climb and listening to the mutterings of others on the ability of my (Ironman) friend dropping everybody whilst still on his big ring. I'm not in the same league as my friend but I'm (now) noticeably a stronger rider than I was.
To convince myself I have created a private Strava segment on my Long Lane training ride where I can compare my times on a stretch of road that I try to power up. I don't have a power meter but Strava claims I'm generating 590 watts and, of course, I'm KOM (since it is a private segment).