How start working out after a long break / how to stay motivated

I've been working out with FB for 20 months, but the last month has been super hard! Took 2 weeks off because of a work trip, then when I came back home I got a cold and I didn't really have the strength to work out + I couldn't breathe properly. After that 3 week break (a month ago) I haven't been as consistent as I was before or eating as healthy as I was doing before.

I was working out 5-6 days a week and now I'm doing 2-3, feel super unmotivated, especially because I feel like I'm weaker than I was before the time off! Can't lift as heavy as I was lifting + I get exhausted with 30 min. workouts and I was doing 60+ min. workouts :(

Any tips? How do you guys get back on track after a break?