The Scots finished fourth in Group A with three wins and two draws from their 10 matches but Martin feels the performances were much better than the points tally of 11 suggested.
"We have been unlucky with a couple of results but we have played well - the performances have been there," said Martin after Tuesday night's 2-0 win over Croatia.
"If the performances are there more often we will get the results. That is what we have got to concentrate on.
"We have got a couple of good friendlies coming up so that is another chance to get together.
"All the time, the squad is getting stronger together. The belief is there in the way we want to play.
"The manager (Gordon Strachan) has instilled that in us. We have got a realistic set of lads with realistic ambitions.
"But we want to play in a major tournament eventually and it is up to us to do it."
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