Mahjong is life
In riichi mahjong, every move you make is potentially fatal.
Every turn you must discard a tile, and every time you do so you risk another player immediately taking away all your points, ending the game and leaving you in last place. It doesn't matter how carefully you plan, how expertly you weigh the delicate balance of a slightly improved hand against the risk of losing it all, or how much time the four of you spent setting up the board, it could all be over in an instant, and you find yourself plummeting down the rankings again, wiping out the gains of maybe a dozen hard-fought games where you managed to mabye not win but at least not come last.
There are some rare situations where you can make a move that is guaranteed to be safe, but they are so far and few between that they are hardly worth considering. The only obvious situation is where you discard the same tile that the player before you has played; the other ones all include situations deep into the game where the majority of tiles have been discarded and one or more players have opened their hands, giving a little more information on what's going on.
Mahjong is what game theorists call a "game of incomplete information". Unlike something like chess, where everything happens out in the open, you start out knowing absolutely nothing about what kind of hand everyone is building. As the game unfolds and tiles are discarded, patterns become visible, plans are formed and abandoned, as the balance of potential risk and reward shifts and makes certain winning conditions more or less likely.
You will come to understand the true meaning of regret, as you confidently discard a tile that would have given you a high score but it needs another one, only one of which is left in the game, and what are the odds? Inevitably you will draw this very tile on your next turn.
The next game you may be sitting on the easiest wait in the world, with a hand full of yaku and several dora that only needs a 1, 4 or 7 to complete it, 11 of which are still in play, and you are in the east seat, so you call riichi, and... someone completes a lousy open tanyao for a lousy 1,000 points. If only you had known!
The first time you are in a south round and you realise that you have accidentally called pon on the east wind and you have no chance of completing a winning hand, the blood will run cold in your veins as you contemplate that the only thing you can do now is to pray for someone else to have even more terrible luck.
Be glad it is only a game.
(Sanma, the three player variant, is much, much worse. If a standard riichi hanchan is a four-way duel, sanma tonpuusen is more like Russian roulette.)