I know that feeling too well. Not (yet) with Surviving Mars, but plenty of other things.
As long as you actually feel good afterwards, I mean, sometimes you need to unwind and taking time to just relax and do "useless" things is OK.
My problem these days tends to be that I feel like I've wasted the entire day, and feel unhappy during and afterwards, yet still can't motivate myself to go do anything (else, or just anything at all, sometimes).
I know that's depression making me feel that way? But it doesn't help in actually solving anything.
If you're finding yourself just wasting time and feeling bad about it, try to take action and talk to someone about it before it gets worse - it's a stres sign your mind isn't properly unwinding or recovering.
If you had fun but just feel guilty about not doing something "useful", consider that self care also means allowing downtime and decompression and sometimes doing little or nothing is OK.