Life consists of positive and negative features, and I think that it is permissible to write about both.
I write four or five a books a year. That means that I usually have one on the go. I am fortunate in being able to write quickly - 1000 words an hour.
I write four books a year. I'm very fortunate that I write quickly; around 3,500 words a day. Being strict about delineating my writing time and personal life, as well as keeping distractions at bay, is the only way I can accomplish this.
If you want to write, do two things - read lots of books and also, in your own writing, practise. Just write and write and then write again. persist. And never be put off or discouraged. You can do it!