How do I choose joy everyday, instead of resentment and anger?

Thank you very much for asking your question regarding your emotions, it's a very interesting, meaningful and important topic for all human beings, as we are speaking about one basic pillar of our lives. 

Basic emotions (Fear, Anger, Sadness, Disgust, Joy and Surprise) are common for many animals, including us, because they are natural (they are not learnt) and they are adaptive, which means they are there to help keep us alive and adapt to the changes of the environment we are living in. What does it all mean? That it's important to listen to them and take them into account. 

In order to do this, I would recommend always assessing the experience of your emotions in a rational way. As you describe after your question, there are many good things going on now that you can focus on, but there are also many other things you are lacking and it's normal that it brings you certain emotions. In this sense, I honestly encourage you to explore new ways to enjoy yourself a bit more and, perhaps, socialise and make plans if possible, so you can address that loneliness. Besides, you could add to your daily routine some exercises of self-improvement (assertiveness, self-appreciation, sports, hobbies, meditation, etc.) that are very helpful in terms of improving your self-esteem and your self-confidence. 

Working on all this together will allow you to feel better and happier, so you won't have as many unpleasant emotions towards your partner and your current situation. Actually, you will feel more grateful and enjoy more your time at home and with your partner. 

I honestly think you can achieve this, you only need to assess your situation rationally and in a realistic way, so you can plan your long-term goals. Then, you can set some short-term goals (weekly and daily), so you approach your objectives little by little. Once you have your plan, try to stick to it and believe in yourself. Finally, remember always to be nice and kind to yourself during the whole process and try to keep it forever, being your own best friend is one of the most important things to be able to achieve anything. 

I hope it all goes fantastically for you. Wish you all the best.