Story idea:
The main character, let’s call him Marvin, is legally in his 30s, but looks about 50. It opens on the funeral of his older brother. Marvin is devastated at blames himself for his brother’s death. The story then flashes back to Marvin’s youth. When Marvin was 16, an 18-year-old version of himself went back in time to show him how he could travel through time to any point in his own life. Marvin uses his power for selfish gain at first, but also to avoid errors. He keeps running into future versions of himself who advise him not to date person X or follow career path Y. Marvin ends up living in an odd loop where he advises past versions of himself to do things without knowing why. He just does it because he remembers future versions of himself doing that to him.
Using his abilities, he’s able to save lives, property, impress people, and do well for himself. However, Marvin also avoids all of the pain and heartbreak that build character, so he finds himself unable to deal with the minor issues in his life or hold on to friends no matter how hard he tries. He also misses out on chances that he would have taken otherwise and so never has quite that exciting of a life, despite the fact that he has abilities nobody else does.
One day he’s sitting at home with a revolver, waiting for a future version of himself to arrive to stop him. None does. He picks up the gun just as his brother knocks on the door. His brother stops him and they have a heart-to-heart, and Marvin decides not to kill himself, but also not to ever travel back in time, no matter how much he wants to: it has led to nothing good in his life.
True to his word, Marvin doesn’t travel back in time. Soon enough, bad things start happening to him and he just rolls with them. He starts building stronger relationships. First with his brother, then with his brother’s friends, then with his own. It’s hard for him at first, but eventually he realizes that this is what his life had lacked: failures, but also unexpected successes.
Tragically, just after Thanksgiving, his brother gets into a car accident and dies. Marvin knows he let it happen and realizes that he cannot undo it, as all his life he’s been unable to change the past.
The short story ends with Marvin going back in time for the last time to say goodbye to his brother. His brother comments on how Marvin’s not as much of a dick as he used to be and bemoans the many years of estrangement they’ve had. Marvin concurs and asks him to start hanging out more often. He leaves and asks if his brother could go visit him that evening. Coincidentally, that evening turns out to be the night the Past Marvin had planned to commit suicide.
Ironically, he didn't see it coming.