Although it is permitted to learn Torah for ulterior motives, it is highly preferable to study Torah for its own sake, without seeking external benefits. However, the enjoyment a person has while learning does not detract from his purity of purpose, and he is not considered one who is studying not for its own sake. This is because the enjoyment itself connects a person to Torah, and that is the main goal of Torah study.

I have heard some people straying from the path of logic with regard to the study of our holy Torah. They say that if one studies, perceives new insights, and rejoices and delights in his study, that study is not undertaken for its own sake to the same degree as it would be if he studied superficially, did not derive enjoyment from his study, and did so only for the sake of the mitzva. [This is because] one who enjoys his study mixes his own pleasure into his study. In fact, this is a well-known mistake. On the contrary, the primary aspect of the mitzva of Torah study is to rejoice, delight, and enjoy his study, and then the words of Torah will become absorbed in his blood. Once he enjoys the words of Torah, he becomes attached to Torah…. I agree that if one studies only because he enjoys his study and not for the sake of the mitzva, that is considered study not undertaken for its own sake…. But if one studies for the sake of the mitzva and enjoys his study, that is study for its own sake, and is entirely sacred, for the enjoyment is also a mitzva. (Rabbi Avraham Borenstein, Eglei Tal, Introduction)

Before a person begins to study Torah he should spend at least a short time contemplating the fear of Heaven. Fear of Heaven is like a storehouse which is necessary for the storage of grain. If one studies Torah without fear of Heaven, the Torah he studies goes to waste.

Torah needs a proper receptacle that can contain it:

It is certainly impossible to say that there is no need for purity of thought and fear of God in order to engage in Torah study, God forbid. For we have learned in an explicit mishna: “If there is no fear, there is no wisdom” (Avot 3:17). For fear of God is the storehouse for the holy Torah that allows man to retain it. If he does not first prepare a storehouse of fear of God, the abundant produce of the Torah will be as if it is lying in the field, accessible to be trampled by the feet of oxen and donkeys, God forbid, and he will not retain it at all.

Before Torah study one should consciously intend to connect to God:

Whenever a person prepares himself to study, he should spend at least a short time in contemplation, with fear of God and a pure heart, confessing his sinfulness from the depths of his heart. This is so that his Torah study will be holy and pure. He should intend to cleave to the Torah through his study. In this manner he cleaves to God, as it were, for God and His will, expressed through halakha, are one. (Rabbi Ĥayyim of Volozhin, Nefesh HaĤayyim, 4:4–6)

When a person exerts himself in his Torah study he becomes completely connected to Torah. If one invests great energy in his study, the Torah will remain with him and will teach him its ways.

“It is first called ‘God’s Torah,’ but when he toils in it, it is called ‘his Torah’” (Rashi, Psalms 1:2). It can be explained that it is called his Torah because it will instruct him and teach him. This is because one firmly acquires the Torah that comes to him through toil, effort, and exertion. He will cling to it tightly, to the point that the Torah itself will teach him all of its ways. This is not the case if he studies without toil, in which case none of his learning will remain with him. This is what the Sages of blessed memory meant when they said about the verse: “My wisdom too (af ĥakhmati) stood by me” (Ecclesiastes 2:9): “The Torah that I learned with anger (af ) remained with me” (Midrash Zuta, Ecclesiastes 2:9). This refers to the Torah one studied with effort, exertion, and suffering. (Rabbi Menaĥem Mendel of Kotzk, Ohel Torah, Vezot HaBerakha)

One who studies Torah must remember that as much as he learns and understands, there are always deeper levels that he does not yet comprehend. Consequently, one who understands only the superficial meaning of what he studies but knows that there is additional depth, or even one who reads without any comprehension of the material, will receive reward for his Torah study on the condition that he constantly tries to increase his knowledge and understanding.

When a person comes to study Torah, his intent must be that he is studying divine words whose deep meaning is hidden from him. In this way all the Torah that comes out of his mouth will be more pleasing to God than sacrifices. But even if all he comprehends is the superficial meaning of the story, or even if one does not understand at all because he is not fluent in the language and he merely reads the words, he will receive good reward for his efforts. With regard to people like these it is stated: “He meditates on his Torah day and night” (Psalms 1:2). The Sages explained that it does not say “the Torah” but “his Torah,” meaning according to the level of his understanding. Even if one does not know how to connect the words, if he is involved in it day and night he will receive his reward and his actions are deemed significant, provided that he constantly increases [his Torah study]. (Rabbi Yeshaya Horowitz, Shenei Luĥot HaBerit, Bayit Aĥaron)

There are those who expend great resources on traveling the world and they pride themselves on having visited many different places. Similarly, it is proper for a person to have at least a superficial familiarity with a wide range of works of Torah, such that he can say, “I was there.” In the World to Come he will be reminded of what he learned in this world.

It is fitting for a person in this world to peruse all the sacred works and learn them all so that he will have been everywhere, just as there are great aristocrats who expend great resources traveling through countries so that afterward they can proudly say that they were in those countries. Just as it is common for aristocrats to proudly say, “I was in Warsaw” and the like, it is similarly fitting for a person in this world to see every place in the holy Torah so that in the World to Come he can proudly say that he was everywhere, meaning in all of the holy books, as mentioned above. In the World to Come he will be reminded of everything he learned in this world. (Rabbi Naĥman of Breslov, Siĥot HaRan 28)