Virtually all ideologies and institutions are devoted to a gender binary that has no room at all for people who do not fit it. As a result all facilities, processes, and designs are made in ways which are completely blind of the needs of people in transition. This makes a lot of things difficult, risky, or essentially impossible to do if you are pre-op or non-op transgender. Here's a few of them; people are welcome to add more in comments.
- Travel on an airline. If existing procedures didn't make it fraught with risk, imagine what it will be like after the TSA finishes installing new scanners which basically see right through all layers of clothing.
- Pee in public. I've heard too many accounts of run-ins with rude, ignorant, transphobic security guards to ever feel safe doing this, even in nominally trans-friendly spaces. Actually, this can even happen to cisgender people, if they are perceived as trans, as happened in two high-profile cases in the last year.
- Swim in public. Unless you don't care if a wet bathing suit makes you non-passable, or you've taken extra heroic measures to compensate.
- Fall in love with someone you meet at random. Meet someone you really dig at work, or in an online forum, or at a bar? Unless they just happen to be one of the few people who are willing to consider a transperson as a viable romantic partner, they are going to reject you when you have "The Talk."
- Work out at the gym. Unless you can arrange special locker room and shower facilities, this could be very complicated.