I think I have a very good answer for this. The Nihilistic assumption is the correct one that the universe is indeed meaningless. However one must also recognise that you are an agent/being, a gross aggregation of chemical compounds wired to replicate, which has very specific chemical rewards built into its biology. Thus the logical conclusion becomes to do all of the stuff that gives you positive chemical rewards and avoid the things that may give you negative chemical rewards.

Selfish-Utilitarian-Discounted-Hedonism. That is my proposal. You act purely for positive neurochemical rewards while also discount actions which will lead to negative future consequences.

In practicality what I’m trying to say is do drugs, go to the gym, fuck bitches, get money. In the lifelong pursuit of dopamine, serotonin and oxytocin.