Is there a trading platform that you can set a limit to the number contracts you can have on at one time? I'm using Quantower right now. I want to limit myself to 3 contracts on any one trade. In the heat of the moment I have been known to get trigger happy from time to time. I guess it could be done by increasing initial margin through my broker but they refused.

I know you can in the Tradovate platform. This is the help page link. As the settings are in your platform you can also lock your Account Risk settings so they aren't available till the end of the session.
https://tradovate.zendesk.com/hc/en-us/articles/360035752033-How-do-I-set-a-Position-Limit-on-my-account-

I think Rithmic R trader also allows for risk setting so if using Ninjatrader on Rithmic data for instance you could also have R-Trader open controlling risk.

Some brokers will set maximum daily loss limits if you ask them, I imagine they could also set maximum position limits. If you decide to change broker, give your proposed new broker a call before opening the account and I am sure if they are keen for your business they will help if they can.

Thanks very much for your reply. Unfortunately Tradovate does not accept Canadian accounts but I will look into your Rithmic R Trader suggestion.

kvnbrn 

In the heat of the moment I have been known to get trigger happy from time to time.

It's good that you are aware of this issue and seek a solution. But I think you're looking for the wrong one.

Of all the psych issues we need to deal with in trading, this is the easiest.
Simple: Decide that you DO NOT ENTER MORE THAN 3 CONTRACTS. EVER. NO MATTER WHAT. PERIOD.
There's no "grey area" in this dilemma.
If you can't keep this simple black-and-white rule, what chance do you stand with the dozens of more judgement-based issues that trading involves?

I trust that you are able to do this. And I urge you to choose to do this, if you have any determination to succeed in the challenging path in front of you to become a trader.
Don't choose the mechanical solution, and then "allow" yourself the "luxury" of being the person who bends the rules but has a machine to stop them. Instead, decide you don't want to be that person any more. Choose the solution that helps you grow into a serious and responsible trader.

Good luck!

Sierracharts allows you to do that per instrument for both orders and trades.