If you want to be happy one day, become drunk. If you want to be happy one year, become married. If you want to be happy all your life, become a gardener. I took away - as the saying goes. If you add "as" the saying goes, it is no longer a sentence. It becomes incomplete. You could say "the saying goes..." but lets just say the saying. I think it would be more unique if all there have the same word... be, get or become. Get does not work with gardner. Be does not work with the first two very well - become seems ok. The repetition of the same word is just a fun way to have it read. I also worked on your capitalization and punctuation.

Its all to do with time and place. You can be happy for a day if you get drunk but the next day you will feel awful. The second phrase is very cynical implying that you can only be happy for one year of your marriage. The third phrase denotes that by tending the land you are always happy because you are not interacting with other people.

If you want to be happy for a day, get drunk. If you want to be happy for a year, get married, But, if you want to be happy all your life, Be a gardener.