Friday drift is the pattern of materially-worse trading on Fridays compared to the rest of the week. Several converging causes typically produce it:
- Cognitive fatigue — by Friday the trader has spent four days in front of charts; decision-quality drops measurably.
- Weekend-squaring — closing positions early to avoid weekend gap-risk leads to suboptimal exits.
- Lower liquidity / wider spreads in many markets late on Friday afternoons.
- End-of-week boredom — the desire to 'wrap up the week with a green close' produces forced entries.
The detector compares Friday-only trades against the Monday-Thursday baseline ON THE SAME USER. The card emits only when Friday performance is materially worse — a Friday that simply tracked the rest of the week or outperformed isn't a behavioural problem and the card stays silent.
Weekend trades (Saturday / Sunday) are excluded from the baseline. They're a different behavioural mode (24/7 crypto, news-driven re-entries) that would muddy the Mon-Thu reference.
Over the analysis window: 12 Friday trades averaging −€8 per trade vs 48 Mon-Thu trades averaging +€10 per trade. Friday win-rate 0%; Mon-Thu win-rate 100%.
Severity bands on the Friday vs Mon-Thu gap: - Mild — Friday is meaningfully worse but still in the same direction (e.g. Friday +3 vs Mon-Thu +10). Note in the journal; one slow week per month is human. - Moderate — Friday is well below Mon-Thu (well under half the per-trade P&L). The pattern is established. Halve the Friday risk per trade. - Severe — sign-flip: Friday loses while Mon-Thu wins. The cleanest behavioural signature. Stop new entries on Friday until the rate normalises over a fresh month.
The Onyx-Engine assigns the gap to one of these bands; the cutoff thresholds are TradeOnyx-internal calibration.
The fix is mechanical, not motivational. Two interventions reliably help: 1. Friday risk-half — set risk-per-trade at 50% of normal on Fridays only. Lets you keep trading without the magnified loss footprint. 2. Friday cutoff time — define a clock-time after which no new entries open on Fridays. Most users find the early afternoon is the right cutoff (the post-lunch + thin-liquidity zone is when the drift typically lands).
Pick whichever fits your routine and write it into the journal as a hard rule.
Tier: Pro. Behavioural-discipline axis. Co-fires with Overtrading (TRA-220) when the user trades MORE on Fridays AND worse — both signals point to the same root state.
How to read the card:
1. Hero (left) — avg P&L per Friday trade with severity verdict. The single number to commit to memory. 2. Two MicroStats — Avg P&L Mon-Thu (the baseline you want Friday to match) and Friday win-rate (the secondary signal — a Friday with positive avg P&L but very low win-rate is a different problem worth flagging). 3. Hint line — the two mechanical interventions (risk-half OR cutoff time).
Re-look frequency: weekly. The Friday signature stabilises after ~6-8 trading weeks. Don't chase a single bad Friday — the detector waits for the pattern.
Tier: Pro.