Choosing what is leads to happiness.  Our usual state is to want things to be different from what they really are, and to think that when only this changes or that changes, then things will be great.  When I find the right partner, when I get that new job—then I’ll be happy.  I like to tell my students that most people spend their lives thinking “if only, if only, if only – dead.”  We spend our lives waiting to be happy, and one day, one moment, it’s all over—and we were never truly happy.
Choosing to be with the moment, to be with what is, that is real happiness.  Even if “what is” is not what you want, and you’re also actively choosing to change, staying with the reality of what is can bring happiness.  And it’s fun!  I know a woman who doesn’t like her tendency to keep going over things in her head, to keep worrying, to be indecisive.  Now, what she could do instead is to tell herself:  “All this stuff that I turn around in my head, I chose this, this is great.  One of the things I really like about myself is that I’m just so indecisive—it’s beautiful.  This is where I’ve come to, this is the kind of person I am right now.  This is what I chose.  Maybe I’ll choose something else, but right now, that’s where I am.” 
Try it.  This should be a very enjoyable thing, no matter where you are, you should be enjoying choosing what you’ve got.  Be alive now, don’t wait until tomorrow.  Tomorrow you’re dead.  Enjoy your life, appreciate your life, choose to be with your life as it is right now.