Is it terrible to quit 2nd job after 3 mths?

[pancakeoarmams]

I recently took on a second job, mainly to help with cost of living etc. I have now been in the post 3 mths but I'm
Exhausted. I'm
Working full time in my main job then rushing straight into my new job 3/4 nights a week until 9pm. I have young kids who need me and a busy husband so the job is becoming too much but I feel so bad leaving after such a short time and letting them
Down 😕

Of course it's not terrible, it's just not working for you.

No it’s perfectly fine
You have to do what best works for you x

Totally understandable. Just let them know it's not working; if they're decent people, give them a bit of notice if poss (or not if you're at breaking point and there's no contractual stipulation) and go.
Maybe you could look out for more occasional freelance-type shifts somewhere (don't know what you do) if you really do need more money.
All the best and full props to you for putting in that energy for 3 months op