OP, if it makes you feel any better, I went back to work full time at 16 weeks with both my kids and you know what I did in the week leading up to my return? Put them into childcare for a few hours so I could lie on the beach to top up my tan and get my hair and nails done. Do I feel bad? Do I fuck.
My kids are my world but my feelings and my wants don't cease to exist just because I pushed 2 6lb bowling balls out my vagina. I don't see anyone telling my husband that he should feel bad if he takes time out to go and play golf because one of our kids cries if he leaves the house.
Babies cry. Because they're babies. It's what they do. If I tied myself to them 24/7 just in case they whimpered, I'd never leave the house and I'd be a hot mess. And not in a good way.
Take the time for yourself, it will help you breathe and reboot and probably, like in my case, make you a more effective parent. Motherhood isn't supposed to be a prison sentence. And like I said on another thread, I don't do mother guilt. Its a wasted emotion, designed to prey on our fragile apparently hormonal state. Instead think about your decision rationally. Your baby is 7 months, a time of pretty normal separation anxiety - it is more than likely that your baby will cry for approximately 2 minutes and then a big shiny new toy will be waved in her/his face and POW, you'll have been forgotten 
You will feel refreshed and invigorated from having some time to yourself where you can switch off and not have to think about if the baby has another tooth coming through, or if they've not hit a random milestone. Instead, you can get on a treadmill, plug in some ace music and pretend you're running down the beach in a stunning bikini whilst passers by quail at your beauty and running prowess.
It's ok to have time to yourself, whenever you need it. It is not selfish to still have your own plans. Your life doesn't stop just because you have become a parent.
Take that hour - maybe next week make it 2 hours and go and get a massage. It'll probably do you the world of good 