Why are these simple concepts so hard to put into practice?

I told you I react before I think. That I snap at my husband daily. Everyday I plan on doing better and I don’t. I get particularly pissy when he is drinking and I am not. I have decided that instead of mouthing off at him I will sit and do thought downloads. Write down what I think instead of saying them. Think before you speak…not exactly earth shattering news. But, I don’t do that. I speak first and think after..but you tell me that isn’t true. So, I am going to have to slow down, take a breathe, take a look at what I am thinking before I speak. Sounds so hard!! Any other advice?