I have to be honest, after 16 family vacations to WDW in 15 years I STILL have to remind myself to take things easy there sometimes. Some things we do that that help us be more laid back. YMMV:
* Don't get park hoppers. When we have hoppers we find our thoughts being tugged toward what we could be doing elsewhere, or trying to cram more into the day than we should. One park per day helps us to "enjoy the now" and be much more zen about the whole enterprise.
* Arrive at park opening (or close to it). Even though I don't schedule FP+s until 11am or later, it helps to be in the parks early to do some rides with low crowds. However, we try to avoid a manufactured sense of urgency about being somewhere before rope drop. If a bus is slow or we are just a little pokey and don't get around until 20-30 minutes after park opening, well that is all well and good too.
* Schedule FP+s for mid day. As alluded to above, mid day FP+s help us miss large queues. If we get extra FP+s later that is great, but if not we are still going to have an awesome time in the parks. After all, there is always Carousel of Progress! (or in a total pinch, Downtown Disney)
* Let the kids stay in the park a while without Mom and Dad. Our kids are now 18(next week) and 15, so for the last few years they just keep their high-energy selves in the park until closing, while the old people (me and DW) go back to the resort and have a proper rest for the afternoon on most park days. This empowers the teens and helps everyone have a good frame of mind throughout the vacation
* Schedule some TS meals. If this can be part of the budget, it really helps the mood of the whole vacation. At TS meals we take our sweet time fueling up, telling stories, making plans, and just generally strengthening bonds of family love in a somewhat relaxed setting. Eating as a family around the table as often as possible is a priority for us at home, so why wouldn't it be while at WDW?