Negative utilitarianism differs from deontological ethics in that it recognizes that no actions are inherently right or wrong, but instead their moral status depends on whether they increase or decrease suffering of sentient beings. It doesn't condemn actions which have no obvious influence on the amount/intensity of suffering of sentient beings, such as playing games or watching movies. Theoretically it would mean that they are morally neutral.
I would argue however that from a purely negative utilitarian standpoint, it would be moral to do things you enjoy if it allows you to keep on living and undertake other actions to prevent sentient beings from suffering. It seems to me that one shouldn't accept the view that they are masters of themselves and are able to immediately do whatever they will. The vast majority of people won't be able to just read about negative utilitarianism one day and then devote their entire lives to reducing suffering. It simply wouldn't be possible, as humans have evolved to do whatever is needed to pass on their genes, which usually means being selfish, not to care about suffering of all sentient beings. I believe that the laws which govern human nature are just as strict as the laws of physics - they are the very same laws operating on a different level, so to speak, and trying to go against them on purpose would be counterproductive. I think that anyone who subscribes to negative utilitarianism should focus on doing what they can, not strive for an unachievable ideal and do less good as a result, as that would be against the utilitarian principle.
I understand that this suffering-focused view of life may seem cold and simply unappealing. At first glance it may look like the ultimate goal of negative utilitarianism is unachievable, thus making any effort towards it pointless, but it really is just a matter of what one focuses at, not what negative utilitarianism actually demands one to do. Being realistic about what you can do is crucial to actually doing anything.
It is also worth noting that, since presumably you are also a sentient being, reducing your own potential suffering aligns with the goal of negative utilitarianism - that includes taking care of yourself both physically and mentally.
I hope I could be at least somewhat helpful.