Life, past, present, future, is all plenty to be sad about. But life is pointless if you can't overcome this.
It is humanities greatest default setting to be negative. But to think positive is a skill that is absolutely needed to live life to the fullest.
I know there is no god, I know there is no higher purpose to me being here, I know there is no such thing as fate or destiny, I know that everything that has a beginning has an end, I know that I am just a sack of some very clever cells that have arranged themselves in such way that they form the most advanced life form on the planet, I am aware that all my thoughts, memories, emotions and impulses are nothing but chemical and electrical reactions happening in my brain, I know that at any moment shit can go wrong, I know that I am infinitely luckier than a person that was born 100 years ago, I know that I'm lucky to not be born in a war torn hell hole, I know i'm lucky to even have access to the amazing peer-to-peer communication platform that is the internet, I know that there will definitely be an incredibly devastating war in my life time that will effect me no end.
And with all of these things being a sure thing in my head, I am happy. I am very, very happy. because against all the odds, I survived, and I am free, and able to choose my own destiny. I am happy that I am intelligent, and have a reasonable chance of finding a mate, in which to pass on my seed, I am happy that I can post this comment, and have my views read by potentially millions of people, I am happy that I have a broad sense of humor, I am happy i'm not a total failure drug addict, etc.
Get over it, life ain't that bad. Unless you're a failure drug addict of course, in that case, hope over to Switzerland. They have an awesome range of exotic clinics.