I don’t have time for this.
It sounds a lot better when you say instead.
I have made a decision not to invest time in this.
That is a more honest thing to say. It also shows awareness and determination. It denotes you are in control of how you spend your day and it holds you responsible for the things your are not doing.
Time is not an entity we can control. What we do with it, instead, is something we can learn to master.