You're not "damaged" because you had a terrible job. This is as common as dirt. Don't take it personally and don't let it affect you emotionally. Almost everyone has had one. If you can afford to take two months off to do recover, do so. If not, then find a job that will allow you to work 9-to-5 and recover on your own time.
On work hours: most startups will have occasional spikes, but well-managed ones will try to keep a 40-45 hour per week average. When people are working 70 hours per week, the quality of work deteriorates quickly. It's a really short-sighted strategy. There are a lot of startups that push people to work 70 hours, but most of those are going to crash and burn.
Also, what happens to most people as they get older is that they have mostly negative work experiences, because most companies are badly managed, and they learn things to avoid. People learn things with experience like, "Working 70 hours per week for months on end doesn't actually work out well." IMO, that's what the 20s, for the smartest people, are actually about: watching people in power fuck up so you know what not to do when you're in charge. Eventually, you'll be in a position to do things properly. It might take a while.
Some things to avoid, going forward: (1) Don't take jobs where the company isn't willing to tell you what you'll be working on. That usually means you're going to be allocated to the least desirable projects. (2) Stay away from the VC darlings, which have (as of 2012, mid-bubble) been infested in MBA culture and are companies in which you're likely to get some insultingly low (~0.01% equity) "profit sharing" offer while making 60 percent of market salary. (3) Don't take an offer just because it's "a startup". Most of these hot startups won't exist in 5 years. Evaluate the job based on the people you'll be working with and the type of work you'll get, not the size of the company. (4) Don't think you're desperate or that your negative experience makes you less qualified for the types of jobs you actually want. Negative experiences are very common, and it gets easier to recover from them as you get older. (5) On job interviews, don't discuss the negative experiences or the bad employer. At all. Bad job experiences are too common to deserve the "silent shame" stigma, but nonetheless, a job interview is just not the place for that. Keep the conversation positive and focused on the future.
For the record, I don't think it actually matters what size of company you work for. There are groups within large companies doing amazing things, and there are awful startups. "Bureaucracy", in the toxic (rather than mildly annoying) sense, is about power dynamics and I've seen dysfunctional relationships in small companies and much as large. In 2006, it was pretty clear that startups were the place to go if you wanted to learn a lot quickly, because we were coming off a bust, startups were undervalued by labor as much as investors, and there were a lot of challenging technical problems in small companies. I don't think that's as true now as it was then. In Real Technology, yes, that's still true; but most of these VC darlings in "social media" are a joke and you won't learn much in them.
What seems to be a trend, in 2012, is that a lot of large companies are developing small and mostly-autonomous groups that I think of as akin to "honors colleges" in order to get a level of talent that would otherwise go exclusively to academia, finance, and startups. Right now, I think the VC startup scene is played out and these honors colleges are a better avenue.