I think, the top three answers by Joe, Anthony and Bigh are giving you all the detail that you need on a technical sense. Although I would like to add a simple picture that underlines, that you can not really compare day trading to long-term trading and that the addictive and psychologic aspect that you mentioned can not be taken out of consideration.
The long term investor is like someone buying a house for investment. You carefully look at all offers on the market. You choose by many factors, price, location, quality, environment, neighborhood and extras. After a long research, you pick your favorites and give them a closer look until you finally choose the object of desire, which will pay off in 10 years and will be a wise investment in your future. Now this sounds like a careful but smart person, who knows what he wants and has enough patience to have his earnings in the future.
The short term investor is like someone running into the casino for a game of black-jack, roulette or poker. He is a person that thinks he has found the one and only formula, the philosopher's stone, the money-press and is seeking immense profits in just one night. And if it does not work, he is sure, that this was just bad coincidence and that his "formula" is correct and will work the next night. This person is a pure gambler and running the risk of becoming addicted. He is seeking quick and massive profits and does not give up, even though he knows, that the chances of becoming a millionaire in a casino are quite unrealistic and not better than playing in a lottery.
So if you are a gamer, and the profit is less important than the "fun", then short term is the thing for you. If you are not necessarily seeking tons of millions, but just want to keep your risk of loss to a minimum, then long term is your way to go.
So it is a question of personality, expectations and priorities.
The answer why losses are bigger on high frequency signals is answered elsewhere. But I am convinced in reality it is a question of what you want and therefore very subjective.
I have worked for both.
I have worked for a portfolio company that has gone through periods of ups and downs, but on the long term has made a very tempting profit, which made me regret, that I did not ask for shares instead of money as payment. These people are very calm and intelligent people. They spend all their time investigating and searching for interesting objects for their portfolio and replace losers with winners. They are working for your money and investors just relax and wait. This has a very serious taste to it and I for my part would always prefer this form of investment.
I have worked for an investment broker selling futures. I programmed the account management for their customers and in all those years I have only seen one customer that made the million. But tons of customers that had made huge losses. And this company was very emotional, harsh, unpersonal - employees changing day by day, top sellers coming in corvettes. All the people working there where gamblers, just like their customers. Well, it ended one day, when the police came and confiscated all computers from them, because customers have complained about their huge losses. I am glad, that I worked as a remote developer for them and got paid in money and not in options.
So both worlds are so different from each other. The chances for bigger profits are higher on day trading, but so are the chances for bigger losses - so it is pure gambling. If you like gambling, split your investment: half in long term and other half in short term, that is fun and wise in one. But one thing is for sure: in over ten years, I have seen many customers loosing loads of money in options in the future markets or currencies. But I have never seen anyone making a loss in long term portfolio investment. There have been hard years, where the value dropped almost 30%, but that was caught up by the following years, so that the only risk was minimizing the profit.