I have been taking things too seriously so lately I'm thinking of taking things more lightly.
Why do you want to take things so lightly?
I'm tired of being serious all the time.
If you take things too lightly you may not take care of your responsibilities. Give matters the seriousness they merit.
I still don't think that being serious is the answer.
There are a lot of things in life that you need to be serious about and you need to care about and do your best. You can have fun too but don't push off the serious stuff in your life.