Depends on the marriage.

Statistics say, older Unmarried women are the happiest, followed by older married men........buwahahahahaaa!
Personally, light-years happier now single!

I agree with what others have said: it depends on the marriage. I think if you can manage to get along, enjoy each others company, and live life in the same way (shared likes, hobbies, daily timetable, etc) then you have a shot at being happy. But if, over time, you grow apart and no longer enjoy similar things or find yourselves living different lifestyles or constantly arguing, you may become adversaries, and then it's time to move on.

Based on my personal experience, No. Overall, probably.

Depends on the people.

I think we're taught from early childhood that we can't be happy if we're single and/or childfree. For myself, the so-called American dream of a spouse, 2.5 children and a house with a white picket fence is a nightmare I would do pretty much anything to avoid.