There is often a belief we carry that no amount of evidence seems to dent. I am not good enough. I always let people down. I am unlovable.
The day can hand you plain proof to the contrary, and the belief simply waves it through and stays exactly where it was.
A positive data log is a way of catching that proof before it slips past – writing it down, keeping it, and letting it slowly build into something the belief can no longer ignore.
How to do it
Start by naming the belief you want to work on – the harsh, sweeping one, in its own blunt words. Then keep a running note, on paper or your phone, and add to it whenever the day offers something that does not fit.
- Write the belief at the top, plainly. Something like I am not good enough, or I always disappoint people.
- Through the day, watch for small moments that quietly contradict it. A task done well. A kindness someone showed you. A thing you handled, finished, or simply got through.
- Write each one down as it happens, or at the end of the day. Keep it concrete – what happened, when, who was there. The specifics are what give it weight.
- Resist the urge to dismiss them. The belief will want to call each one luck, or an exception, or not really counting. Note it anyway. That dismissing is the very habit you are working against.
- Read back over the log every so often. Watch the evidence accumulate, and notice how it sits against the belief you wrote at the top.
Done for a few weeks, the log becomes something you can hold in your hand – a quiet, specific record that the belief was never the whole story. It will not erase the belief overnight, but it gives the fairer view something solid to stand on.
Where it comes from
The technique comes from schema therapy, an approach developed by the psychologist Jeffrey Young in the 1990s for the deep, long-held beliefs about ourselves that ordinary cognitive work struggles to reach.
Young noticed something stubborn: a harsh core belief quietly filters the world to fit it, noticing every failure and dismissing every success as luck or exception – the evidence against it is there all along, it just never gets recorded.
The positive data log was his answer – a deliberate, written record of the small moments that contradict the belief, so they accumulate where the mind can see them. It has since become a common tool in everyday CBT, and one of the gentler ones – it works by adding, not by digging.
Worth knowing
The mind isn’t neutral about evidence. It leans, by default, toward what it already believes – a habit psychologists call confirmation bias, sharpened by a general negativity bias that makes threats and failures louder than the quiet good.
So a harsh belief becomes self-sealing: it notices what confirms it and lets everything else fall away, then points to the lack of contrary evidence as proof it was right.
A log breaks that loop in a plain, mechanical way. Once the disconfirming moments are written down, they can no longer be quietly forgotten – they sit there, specific and dated and undeniable, building into a body of evidence the belief has to reckon with. It doesn’t argue with the belief. It simply stops the belief from cheating.
Recommended reading
Jeffrey Young’s own Reinventing Your Life is the natural starting point – schema therapy explained for a general reader, by the psychologist who developed it.
For something more contemporary, Dennis Greenberger and Christine Padesky’s Mind Over Mood is a widely used CBT workbook built around the same evidence-gathering principle, applied more broadly.