It can be trained. If 1 or 2 tables for 15 minutes is all you can manage right now, then go from there and build up. 

ADD?

The Hud will help you get an idea of how loose/aggressive people are but it's not going to help with the tilting. Same as Zen if 10-15 minutes then do 2 tables for 10 to 15 then next time 15 - 20 minutes and build it up slowly. Also maybe do some sort of stop loss, if you lose 2 BI in 5 minutes log out for a bit.

To start off, you first have to learn how to control your emotions at the table, live or online. In order to do this, I would suggest reading some useful strategy books that cover this sorta thing. Tommy Angelo's, "Elements Of Poker" is fantastic and I think it could help you out. I've also heard and read nothing but great things about Jared Tendler's books, "The Mental Game of Poker", both volumes 1 and 2. Tilt control is covered in both of those volumes. 

And second, you gotta try to relax and remain calm while playing live or online. Don't get me wrong, it's good to be paying attention to whats going on around you, and store information from what you've gathered, but do it at a pace from which you can handle. Maybe that even means to ask yourself less questions about your surroundings and opponents, and merely just focus on your own game. I would even suggest to not multi-table online just quite yet and practice these skills 1 session, 1 table at a time. Sometimes it's better to start off like that anyways.

Lastly, if your serious about making decent money from poker, live or online, you gotta be thinking long-term. Might take some time to be where you wanna be playing this game. That's just how it is. For the ones who play this game seriously, they're always thinking long-term, almost like an investment. 

Hope this helps, and best of luck to you on and off the felt.   

I feel like this post was put here just for me! I am a pretty decent tournament poker player (live and online). And if Im not winning, Im losing, FAST. I have won 4 online tournaments in the past 6 months and cashed in about 4 more, But Ive probably lost 50-60. I need to cool my head, big time.

To begin dissecting your mental game issues, 

1.) create a Tilt Triggers- and Tendencies List. 

'triggers' - what specific situations/circumstances/factors leave you feeling frustrated/angry/upset - any negative emotional response (and sometimes even positive ones) are a red flag that there was a trigger.

'tendencies' - what psychological and strategy specific changes happen to you and your game. What emotions do you feel? what goes through your mind? how do you play differently when tilted?

Keep a notebook/document with you and record these while playing

Becoming aware of what makes you tilt and what your mind and body goes through is the first steps to eventual resolution.

2.) Select the ones that you feel are hurting your winrate the most, then do further analysis. These steps are outlined in Jared's MGoP. Basically, you will need to detect the faulty logic and irrational emotional responses in real-time and 'inject logic' when you feel the onset of negative emotional reactions. Eventual resolution means you fully understand and accept things as they are and you no longer tilt. 

3.) Date your work, so that you can see the progress you making. This means that you see results in your game even when you are not making money.

4.) When you feel you have removed enough tilt issues from your game, begin an A-Game journal and now begin improving your best game possible. 

Good luck,

and i will be happy to help you work through some of these, PM me

+100 to tommy angelo books being a good place for you to start with your tilt issues

re focus, I also agree with the others who say make it your goal to concentrate playing two tables for 15 minutes then more and more. tbh there might be a biological problem if you can't do that. do you have trouble concentrating in other areas? (not sure what your other hobbies are). are you playing after a long day of work? or without eating right before? are you 85 years old? hah :) seriously though you really should be able to teach yourself to concentrate and focus. that is a major skill that you need to be a successful poker player (and tbh probably in most professions). there are resources on the internet i'm sure you could look up but that's something you really should work out.

another thing that will help your focus is as you improve in certain areas of your game, some things become a little more automatic, and take less thought. perhaps you are overthinking areas and not coming to conclusions so you are wearing yourself out with questioning and not coming to an answer? sort of frying yourself?

re HUD: i'd say don't worry much about a hud for now but know it's def a useful tool. Start slow with a few of the most basic stats just so you get used to the idea of a hud. i'd work mostly on the tilt issues, focus issues, and your overall game for now. know that your hud is a big part of 90% of pro players' every day game though and it's a pretty useful tool. so just don't dismiss it forever...but just for now you might get more bang for your buck working on the other stuff

good luck.

Tommy Angelo is good for general all round philosophies pertaining to a holistic positive view of the game. i particularly like 'Reciprocality'. 

For concise, step-by-step mental game strategies Jared Tender's books will be best 

I have some similar Problem, maybe it helps to "Stack" the Tables so u didnt See the outcome of the Hand. Just Play your Session without Looking in your Account. For sure it Works better If You Play More than 2 Tables