Confused by calories lol

Hey everybody (:

I know this sounds silly, but I'm new to doing this the healthy/old fashioned way vs. using diet pills like I did when I was 17. Lol

Anyway, I've been using MFP religiously for the 2 weeks & it advised me to consume 1300 calories a week since I am a student from 8 to 12:30 & then a work at home agent from 1 to 10pm. So that pretty much keeps me off my feet a good bit of the time. However, I've finally managed to squeeze some time out of my days off & after I get off at night to work out so I'm wondering do I need to eat back my calories since 1300 is pretty low & I know that your body can't really function on less than 1200. I'm currently running a mile & I'm about to incorporate the 30DS as well. So is 1300 still okay if I eat back the calories I burn or should I up it? I'm trying to tone up some of the flab I've accumulated over the years lol

As of now I don't feel any different or sluggish. I've stopped drinking soda & feel better than I have ever. The energy is awesome!

Also I've read that it's hard to maintain the weight you lose if you eat too few calories to lose it? Is that true? I don't want to lose it all & then gain it all back because I go over 1300 calories once in a while. Lol

Thanks in advance,
Any information would be helpful!

-Jessica