The phrase does a lot of work, and it is worth being precise about where the work stops. A self-repaying loan repays itself at exactly the speed your collateral earns, and not one basis point faster. That is the whole mechanism. It is genuinely good, and it is not magic, and the gap between those two statements is where people get hurt.
Start with the honest failure. If the yield rate on your collateral goes to zero, your debt stops shrinking. It does not grow, because Pillar charges no interest and nothing accrues against you — the number you owe on a dead-quiet year is the same number you owed at the start of it. But it does not go away either. A self-repaying loan is not a loan that forgives itself. It is a loan that is paid by something other than you, and if that something stops producing, the payment stops arriving. Anyone describing this product without saying that sentence is selling you a brochure.
This matters more than it first appears, because it changes what you should be estimating. The dashboard shows a time to zero, and that number is real, but it is a projection from the rate the collateral is earning right now. It is not a maturity date and it is not a promise. If the rate halves, the estimate roughly doubles. We show the realised rate rather than an assumed one for precisely this reason: a projected rate makes a much prettier dashboard and tells you much less about what is actually happening. A brand-new position reports close to zero for a while, which looks worse and is more truthful.
The second limit is liquidation, and it exists because pretending otherwise would be a lie about a lending protocol. Your position can be liquidated. What Pillar constrains is how much: the contract computes the smallest repayment that restores your position to health and reverts anything larger, so a liquidator taking more than that does not get a worse outcome, they get no transaction. You lose a slice rather than the position. That is a mathematical constraint in the contract rather than a policy we promise to observe, which is the distinction that matters on the day it is tested. But a slice is still a loss, and a large enough gap can move you from healthy to liquidatable between one block and the next with nothing in between for you to react to.
The third limit is everything Pillar does not control. The vault that produces your yield is someone else's contract. The price feed is someone else's infrastructure. The venue that converts your yield into the currency of your debt is someone else's liquidity. The collateral token and the stablecoin were both issued by someone else. Pillar can decide how it behaves when those systems misbehave — and it does, by refusing to act on a price it cannot defend, and by reverting a harvest whose swap cannot be filled at a fair rate — but it cannot decide whether they misbehave. A failure in any of them is a failure you experience. And borrowing at all depends on the treasury holding a balance to lend.
There is a fourth thing that is less a limit than a shape you should understand. Your debt only moves in one direction on its own: down. There is no schedule, no minimum payment, and no maturity conversation. The flip side is that there is also no moment when the protocol tells you that you are finished, other than the moment the balance actually reaches zero. Nobody sends you a statement. If you want the position closed faster than the yield closes it, you repay directly, which is always allowed and never penalised — there is no early repayment fee because there is no interest schedule for early repayment to interrupt.
We put all of this on the site rather than in a footnote because of a specific belief about what a risk disclosure is for. A protocol that hides your distance to failure is not protecting you from anxiety. It is protecting itself from your questions. So the health factor, the current loan-to-value, the yield that has already gone toward your debt, the estimated time until it reaches zero, and the percentage the price would have to fall before liquidation are all on the dashboard, updating continuously, whether or not they look good that day.
The product is still worth using. You get cash without a sale, the position stays open, the upside stays yours, and the collateral works while it is pledged instead of sitting dead in a vault. Those are real and they are unusual. They are just not unconditional, and a product that describes them as unconditional has told you something false in the first sentence.