@Val

Val I think Brian has some valuable points. I think that we are often constrained or restricted both physically, mentally and emotionally which in turn limit our abilities. We can constrain, restrict or limit ourselves but we can also be constrained, restricted or limited by other people or our surroundings. 

So for instance if I were constrained by someone and tied up with a piece of rope I would not be able to move and therefore I would be restricted and limited in my movements. 

But what about your English language learning. Are you constrained or restricted from saying what you want to say because you have limited knowledge? 

We could debate this forever :) 

@Brian,

Thanks, it is very helpful.

I'm sure their is a technical way to explain but here is how my English brain thinks of it and how I would use these words:    Limitation - is something that is physical. Like " I have a limit on how much I can eat. I eat one plate and then I am full." 

Restrict is not the total of what you can eat, but what you choose to eat and then stop.  " I am restricting myself to one plate of food so I can lose weight. I can eat more but I will restrict myself to one." 

Constraint is not used as much as the first two. (I am having a hard time thinking of an example...)  " You must use self constraint to only eat a half plate of food if you really want to use weight."  

My only advice is they are more or less the same just have very small differences but I believe you will be understood using all of them. I don't use constraint very often. Limit and restrict much more often.  Hope this helps. 

@Brends,

Can you give me examples where I can use only one of them and not others?

If you are restricted or constrained you are automatically limited. 

This is not an easy one as it really does depend on the context of the situation. :)