When one of you makes a supplication (to his Lord) one should not say: O Allah, grant me pardon, if Thou so likest, but one should beg one's (Lord) with a will and full devotion, for there is nothing so great in the eye of Allah which He cannot grant. (Using translation from Muslim 2679a)
"إِذا دَعَا أحَدُكمْ فلا يقلْ: اللهمّ اغفرْ لي إنْ شئتَ وليعَزِمْ المسألةَ وليُعظمْ الرغبةَ فإِن اللهَ لَا يعظمُ عليه شيءٌ أعطاهُ".