This is true for any single flip isolated from within a set, but when taking the set as a whole, the odds of each subsequent flip change depending on the previous flips. For example, suppose you flip a coin 5 times, the first flip is heads, so the second flip now has a 75% greater chance of coming up tails; if the second flip comes up heads again, the third flip now has an 87.5% chance of coming up tails, the odds are increased by a half each time, and this could theoretically go on forever. If you were to flip a coin 100 times and the first 99 came up heads the chances of the next one being heads would be astronomically small, as would the chances that the first 99 would come up heads in the first place (in fact it's been estimated that nobody who has ever been alive on this planet has ever seen 75 flips of the same face in a row, let alone 99). Yes, it's still 50/50 each time you flip, which is why we started with 50% on the first flip, and why we add half of the chance percentage of the previous flip onto the next one.
