A couple of points:
1) You haven't failed the checkride; you simply need more than one flight to complete it. No big deal.
2) Students don't fail checkrides anyway. CFIs do. If a student doesn't pass, the fault primarily lies with the instructor who endorsed the student as being ready.
Wow, give me a break. At some point the student has to take responsibility for themselves. The instructor can't learn on the student's behalf. This attitude is completely unhelpful.
The student can't endorse himself for the ride. That's up to the CFI's judgement.
I have to agree with
@dmspilot here. Sure a student cant endorse himself but that doesn't mean the student isn't responsible for themselves in ensuring they are ready for the checkride. I know some students who have even needed to be "kicked out of the nest" so to speak; either they were happy with the privileges and responsibilities they had as a student pilot or they were convinced they weren't ready for the checkride, I dont know which but a CFI's endorsement is only a prerequisite to taking the test... Preparing for, scheduling and taking the test are typically all on the student.
I'd also point out that students sometimes DO fail checkrides. It happens. Maybe it was an off-day or something.
I've only had to re-do one checkride but when I look at each of my checkrides, I could easily find things that were not to my normal standard.
On my 2 most recent checkrides:
CPL - I let my heading wander a bit during slow flight. Slow flight and stalls were the one maneuver that my instructor didnt have any real input on because I nailed it so well when flying with him. Slow flight and flying the stall are part of the things that I like demonstrating because so many are freaked out by the very idea of a stall. Yet for whatever reason during my checkride, I was just off; maybe it was jitters or visibility and lack of good visual landmarks due to haze or any of a number of different things but I was very unhappy with myself after doing it... The DPE did comment that I let my heading wander but I did correct it and I still managed to perform within the ACS standard but I was still upset with my performance overall.
CFI-A - The only checkride I've had to take twice. I passed a 4.6 hour oral, went flying for 1.4 hours and came back and had to demonstrate a shortfield, softfield takeoff and landing and a go-around. Knowing how close I was excitement started to kick in but so too did the fatigue of a long and stressful day (delayed 45 min by traffic on my way to the airport, then had to fly 1 hour xc to get to DPE that required an unexpected IFR clearance for the ILS to get in thanks to a broken layer of clouds at 1100 ft, followed by the 4.6 hour oral [6 hours when factoring in breaks and administrative portion] and a 1.4 hour flight that had some higher gusty winds we were pushing on 11+ hours since I had left the house by the time we landed) and I landed long and really dropped it in a gusty crosswind on my first landing attempt which just ratcheted up my anxiety as I could see the checkride slipping through my fingers.
We taxi backed and I proceeded to instruct on a shortfield takeoff during which I uttered the words "accelerate in ground effect." The DPE looked at me and said "what did I ask you to show me/what did you just teach me?" to which I responded with the immediate "a short field takeoff," then he said "are you sure?" so I thought back on it and realized what I said and how I slipped up and told him. Unfortunately the damage was done and he had to disapprove because I taught an incorrect maneuver. Was that my instructor's fault? Nope. It was totally my own. I knew it, I just screwed it up. The DPE knew I knew it but couldnt ignore that I screwed it up. My instructor knew I knew it and when we went out to do the remedial lesson pretty much just went along for the ride. My retest was 0.4 and 3 laps around the pattern.
Sure maybe the CFI can be considered its own entity but I'm sure I could find other mistakes, completely of my own making, in other flights and checkrides...