Mushtaq, 33, played the last of his 52 Tests against South Africa in Faisalabad in October.
But he was left out of the side for the current series at home to archrivals India which is tied at 1-1 ahead of the final Test next week in Rawalpindi.
However, he said watching the series had made him even more determined to get his place back.
"I'm just 33 so I think I've still got two or three good years ahead of me," Mushtaq said at Lord's in London on Friday, where he was playing for County champions Sussex in the English season opener against MCC.
"Now I have to stay fit and keep taking wickets," added Mushtaq who last year became the first bowler in five years to take 100 wickets in an English season (he finished with 103) as he spun Sussex towards their first ever County Championship (first class) title.
Reflecting on the momentous series against India, Mushtaq said: "The second Test was very good from a Pakistan point of view because it showed the team could come back (after losing the first Test).
"Playing against India is one of the best things that can happen to a player. It is something you will remember all your life," the former Somerset and Surrey bowler added.
"God willing, I shall get back in the Test team. Sometimes, even if you are not performing well, He can get you in the side and everyone needs that support," Mushtaq, a Muslim, added.
"It's a pleasure to be back at Sussex. Now I must keep taking wickets and believe in God."