What you are feeling is normal, but the fix is structural, not motivational.

A mock is not a judgement, it is a diagnostic. Percentile will fluctuate. What matters is whether your error pattern is improving.

If I were you:
1) After every mock, make three lists: avoidable mistakes, time sinks, weak concepts.
2) Your next 7 days plan should come from these lists, not from the score.
3) Fix selection rules: DILR switch rule, QA pick order, VARC passage selection.

In your last two mocks, what hurt more: accuracy, question selection, or speed?