It's okay to take time for yourself. In fact, I think that it should be a rule. This doesn't mean that you don't enjoy your time with your baby. There are just simply moments when you need to speak to another adult; not think about nappies or about managing naps and meal times.
If you can, go out; even just for an hour. Leave your baby with Dad or another person you feel comfortable with. Get a coffee, go for a walk, a run, window shopping...whatever works for you. It can be surprisingly difficult to do it for some people. Some have to start by going for a small amount of time and build up, others feel really fine with it. But I guarantee that you will come back a better mum for your little one as a result.
Some weeks though, it's just not going to happen. Either your partner is working mad hours and the people you feel comfortable with looking after your little one aren't available, or your baby just needs you around. In those times, taking time for yourself in the house just has to do. For instance, when your baby is napping or has gone to bed, ignore the house chores and just sit down or even take a nap!? In those early days, achieving this can be difficult because baby, quite rightly, needs most minutes of the day! At those times I found that taking time for myself had to be those moments when I did the simple things, like putting perfume on, or something like that, and recognising that that moment was for me.
This is not meant to sound selfish and there are times when you might just have to see it through and know that there's some time for you coming up. But after years in the job and now having been a mum, I know that taking care of yourself is actually taking care of your baby too.