So you get home late, need a hug and some food, yet your child refuses to be loving at all, throwing a fit over who knows what instead. Then you have to discipline when you aren't exactly rested and on your A Game, and you end up having a horrible night, full of guilt and a little justified self-pity.
There are a couple of things that strike me in this scenario, and I'm going to be super honest with you. (That means get out your big girl pants and try not to be offended.) First off, I don't know you, but if you're reading this, you are reaching out for help and that in itself is HUGE. Understand what that says about you as a mom...that you want what is best for your child and you will do whatever it takes. That makes you an amazing parent! We all make mistakes, but the best parents are the ones who vow to do better and put some action behind it.
Second, the discipline aspect is a simple enough problem to solve. Research books, video series...whatever you think could give you some very basic places to start and how to understand your child. There are plenty of resources that can help you understand where your child is coming from and how to give them what they need so they act better: ways to communicate, and how to reword what you have to say so that it makes sense to your child and they will respond positively.
The last, and more important point, I think, is addressing your needs. I sometimes hear from parents that they want their child to act more loving and they don't want to be made to feel bad. (Here's where I get tough...) That is not actually a discipline issue. Yes, if you change the way you react to unloving or poor behavior, you will in turn change the child's reactions, and that is discipline. But it goes more basic and deeper than that. As parents, we are there to meet the needs of our kids. But we absolutely cannot expect them to meet our needs. Yes, we need our kids to love us - or at least act loving so that we have some reason to be nice to them - but they are kids. They cannot and will not understand that we have worked all day and busted our chops trying to provide them with a good life. They will only need, need, need from us. So when we get home at 9:00, they will not understand that we need a hug and some time to shovel down five bites of food. They only see life from their perspective and their needs....and they will probably need love (and a glass of water and two books read to them) from you even though you're exhausted and having nothing left to give.
You know all this, but let this post serves as your official reminder. It's not that they don't love us. Their brain just works in a very limited space, and it's all about them. Those happy family images you see on T.V. - kids running and greeting the parent after a long day of work - that's a rare gift, and it generally just doesn't work that way. First of all, to GET kids to a point in life that they look beyond themselves and see or care about your needs takes a very secure, devoted parent, and a boatload of time. Second, life is just crazy and busy and we don't always act our best.
Forgive yourself, keep perspective, and do your best. Remember that kids need us to discipline and provide a consistent, loving environment for them. It makes them feel secure and happy. You may feel like the bad guy today, but if you reflect on the lesson you are trying to instill, and you feel it is appropriate, stick to your guns. Project a loving and firm stance. Long term, you may just find out that, glory be and hallelujah, it worked!