Since school just started I have a feeling my motivation will go down.
Literally this.
I have ideas and I know I want to post... but social life. It's really just a matter of balance and once I find that, I'll be set. Thankfully, I'm only in 2 RPs and one of them in sandbox-y so no one is waiting on me to post and the other I'm waiting on someone else.
I don't usually struggle with motivation, if I do I put on some music and I'll be ready to write. More often than not it usually depends on the RP what my levels of motivation is at. I never want to be the reason people are waiting so if it's a plot-driven RP where you need to interact with other characters my motivation is rather high in those situations. If it's sandbox-y then my motivation is significantly lower because I don't have that push/reason to make me post.