How do you stay motivated?

[Brad Clarizio]

Recently, my rentals have been kicking my butt. I am up to 11, the highest I've ever owned, and in parallel, my career has gotten busier than ever (I work a full time job where significant travel is involved as well). 

I am having a hard time finding motivation lately. I'm rehabbing two properties (rentals 10 + 11), just took over a house after an eviction that is TRASHED (3k+ in repairs), and had a furnace and A/C go out at another house ($3,200 repair because of the time of year). I'm starting to feel like I'm not making any money (I am) because it's one thing after another. 

I get it- I bring a lot of this on by myself because I self manage and continue to acquire- part of me thinks I need to take a break for a year and get remotivated, but the other part of me thinks that the moment I stop, someone else gets ahead. 

I am 27 years old and want to "retire" at 35, so my goal is 20 SFH's- that will allow me to live a similar lifestyle as I do now, but have the freedom I want.

Reel me in here folks- how do you keep going when it seems like it never ends?