My partner has gone on a lot of dates. First dates are stressful for me every time. Second dates, too. It takes me a while to trust that the newbie is going to respect her, respect our boundaries, etc.
Things that help:
1. Meeting her date, getting to know them.
2. Having scheduled post-date check-ins / quality time planned in advance. At this point, it is assumed that if my partner has a date, that we're spending at least part of the next day together.
3. Having friends who know what's going on and can offer support. My support network is pretty small, but I've usually got at least one person I can count on.