The game doesn't do a good job of explaining this, but, there is almost no benefit to min-maxing it. Absolutely nothing is gated off by taking your time to do it. If it takes you seven in-game years to finish the community center, there's no downside. It's a common misconception that you need to complete everything as quickly as possible. I think this stems from the fact that after your second year you get a kind of "grade". But this doesn't matter since you can choose to get graded again whenever you want!

Some people find the min-maxing to be part of the fun, but it sounds like it stressed you out, so you just shouldn't play it that way. Take as long as you want, the game will not punish you for doing that.