How to play 3bet or all in?Lets share some opinions

Here is the scenario:
I am playing in MTT.When blinds are small I 3bet some hands and won with cont. bet.I got 1800 chips now.Hands are passing away and binds are getting bigger.Blinds are now 75-150 and I got 1500 chips again.I have JJ,QQ,AQ,AJ or AK(TT and lower pocket pairs are not worth of playing on FT by my opinion.I have try all in with low pocket pairs to many times and lose in one on ones).If I 3bet and get call it will be 1/3 of my stack.On the flop there is always option to miss and lose hand.After that I will stay with 1000 chips waiting for miracle or to be eated by blinds.Other solution is to go all in and get no calls or get call and hope for best showdown.How to play in this situations 3bet or all in?

Any answer is going to depend on position, players left, chip sizes, tournament type, player tendency's, and other stuff. I'm not sure because I'm a little confused about your post but it sounds to me like there are a few things that can be tweaked.

First, don't be scared to fold pocket pairs before the flop. Low pocket pairs can be folded very easily, if you can only set mine and the blinds are high, its not worth it. Second..when you push all in you have to think about what hands are going to call you. Its rarely going to be a bad hand, especially when stacks are deep. Its a major flaw in peoples games and is all over the place (cash games..big problem). People push with 10s or js or even 2s because they are scared to play the hands. In lots of situations, short stacked or late in a tournament for example, it can be very benificial to push all in. But you have to understand the problem with it. It works well until you get called.

I agree to the first answer you get...
It depends on many circumstances!

I know all that you said.But you know how is when you're playing FT MTTs if it isn't your lucky day you will get something(dealt not floped) in every 20-th hand.I played Stars torneys there is a lot of straights lot of flushes.88,99,TT are great to play all in but on FT with those hands you can limp in and pray for set or to fold.I have been dealt 77 on full tilt for about 10-15 times in session and won 0.I don't even limp those hands it is not worth limping.
I should write bet 3BB not 3bet