For what it's worth, I am not a planner. I dislike the fastpass+ system, but had my fastpasses in place for our trip. I didn't really panic that I couldn't get the attractions or times I wanted because I was fairly sure I wasn't going to be able to keep most of them. I was annoyed that I couldn't get 7DMT at all my 30 days out (AP holder, not staying on property).
Since getting here I've changed my fastpasses daily, if not more. We choose where we're going to go the night before and I change our fastpasses. I have not had a problem getting anything at all. I just checked for tomorrow and soarin is available for multiple times (always the first thing gone in the first tier). I got 7DMT 3 times this week (usually only one or 2 times available though, but I just move the rest around to suit that), and have even gotten Anna and Else two times, letting them go both times.
The only thing we couldn't get was Be Our Guest, but yesterday went on the standby line and only waiting 15 minutes, if that long. We were glad we got to try it, but we both agree the food and the atmosphere were nice, but nothing spectacular.
When this new system started I was very unhappy. And I still don't like it, but I wasn't going to let it ruin my vacation. Unfortunately there's not much I can do about being tied to my phone the whole trip, but it does come in handy when you're informed that an attraction is down via email, so I look at that bright side.
So, don't panic, no crying, it's a vacation. And take a bit of comfort knowing you're not locked out of things because you can't get them now.... Just get whet you can and tweak them to better times and switch attractions up as needed.
And just for the record, if anyone is trying to "fit" a headliner into a certain time between two other attractions, don't. The system will tell you it's not a available if it doesn't have that specific time. Cancel the whole day out and start over. I did this anytime I wanted 7DMT and was able to get a time. I just fit the other two around it and can usually get the times consecutive.