Leaving my 15 month old. How do I enjoy time when I am not with my kids ?

Is it just me or is it really hard to have a life out side your children.?
To be honest my kids are everything to me. I never realised how much you could love someone until they came into my life. The problem is I feel like I can't relax when there not with me. I have wedding coming up and it will be the first time I leave my youngest (15 months old) and I've already started to think crazy things like "what if something happened to me and I died in a car crash or something and he just thinks I've left him)
That's insane right!!!!
We have two kids and I dedicate my life to them and I absolutely love being there mummy but I also feel like my husband needs me to. I want to be able to relax and have a good night out with him without feeling guilty about leaving my little one. ( he will be with my mum who he sees every week)
I don't even really know what I'm asking. Just want to hear of other woman that are the same or have left there 15 month old for two nights?