How do I anticipate everything that could go wrong in a contract?

You draft well now, and the thing still stretching you is foresight, seeing the whole field of ways a deal can sour. That is the hardest part of the craft, and it is the last to come. It does not arrive by being smarter. It arrives by having seen more break. No one imagines every failure from a blank page. The people who seem to are borrowing from experience, their own and others'. They keep lists of what has gone wrong before and run each new deal past that list. It is memory made into a tool, not raw genius. Start your own list of failure points, drawn from deals you have seen go bad and clauses that saved someone. Run your next draft against it. Your foresight will grow the same way everyone's does, one hard lesson written down at a time.