Beginner - Self Destructing

[MagicMan08]

I have been playing serious poker for about 1 year.

It seems lately I have been playing excellent poker, and when I have a decent stack, I have been self destructing.

How can I maintain that focus to be tight aggressive for the whole tournament???

It seems I have been making DONK mistakes the last couple of times?

Is it inexperience of lack of patience or plain and simple stupid moves?

I have had great success and have earned respect among the people I play against as one to analyze someone elses game and I have only been playing for one year.