Can we realise God by our devotion only to Guru?
If you are devoted to your Guru, God-realisation will follow automatically. However, it is better to worship both God and Guru together. But why? The reason for this is that our mind, being under the sway of maya, cannot have unwavering faith in our Guru and so our devotion to him will not always remain exclusive. Because Guru is directly perceivable, our material intellect can sometimes question his actions. The same thing happens during the descension of God, when we see Him directly. This is all due to our faulty intellectual perception. The same is also the case with our Guru. But, on the other hand, we cannot perceive the Supreme Lord directly and so our devotion to Him will never waver.
Thus, only when we are devoted to both God and Guru simultaneously can our heart be purified. Moreover, it is a lot easier for the mind to focus and meditate on the enjoyable pastimes of the Lord. For example, there are numerous pastimes of Shri Krishna, including those during His childhood. One can choose any of the innumerable pastimes to engage one's mind in with feelings of love.
You had once said that till today no one has been able to surrender 100 percent. Whenever I think of this, I feel disappointed.
Well, it is not a matter of one lifetime. The other day you asked something similar. You yourself had said that while performing worldly duties, detachment and surrender becomes more difficult, in fact worldly attachments increase. So the answer is that it is difficult to achieve all this in a single life. However, those who are highly focused and diligent will surrender quicker and can certainly achieve their goal in this lifetime.
When will such a fortunate situation occur for us and what is so special about our next life?
If you are doing devotional practice then you do not have to restart all over again in the next human life. You will be admitted into a class higher than the one you left in the previous human life. You will surely get whatever you have previously earned. Depending on your sadhana, you shall be reborn into the family of a bhakta where you will be in a spiritual environment right from childhood. So there is no need to feel disappointed.
According to the philosophy of the Muslims, they have only one life to live. So whatever they do, it is only for this life. Hence, there is a state of fear in their minds. If someone has earned ninety-nine percent in his life, then that poor fellow will be deprived of his spiritual goal due to a shortfall of just one percent. However, in our Hindu philosophy there are innumerable lifetimes. If someone has earned six percent in this life, then he could reach eighty percent in his next human birth; there is no question of going backwards. We can always move forwards. Whatever we earn in this life is available ready-made in our next life.
Original answers given in Hindi by Jagadguru Shri Kripalu Ji Maharaj