QUESTION: Why can't you love God with all your heart, mind, soul and strength?
ANSWER: Because you are a sinner and incapable of doing one good thing perfectly.
Matt 19:26 And looking at them Jesus said to them, "With people this is impossible, but with God all things are possible." NASU
Matt 21:22 "And all things you ask in prayer, believing, you will receive." NASU
Mark 9:23 And Jesus said to him, " 'If You can?' All things are possible to him who believes."NASU
Mark 10:27 Looking at them, Jesus *said, "With people it is impossible, but not with God; for all things are possible with God." NASU
Mark 11:24 "Therefore I say to you, all things for which you pray and ask, believe that you have received them, and they will be granted you. NASU
John 14:26 "But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all that I said to you. NASU
Rom 8:32-33 He who did not spare His own Son, but delivered Him over for us all, how will He not also with Him freely give us all things? NASU
1 Cor 3:21-23 So then let no one boast in men. For all things belong to you, whether Paul or Apollos or Cephas or the world or life or death or things present or things to come; all things belong to you, and you belong to Christ; and Christ belongs to God. NASU
1 Cor 13:4-7 Love is patient, love is kind and is not jealous; love does not brag and is not arrogant, does not act unbecomingly; it does not seek its own, is not provoked, does not take into account a wrong suffered, does not rejoice in unrighteousness, but rejoices with the truth; bears all things, believes all things, hopes all things, endures all things. NASU

Phil 4:13 I can do all things through Him who strengthens me. NASU

My concern is that your conclusions seem to be based more on your experience (and/or the experience of others) than it is on the Word of God. The Bible teaches us that when we “compare ourselves with ourselves’ we are unwise (2 Cor 10:12). As a result, I should not be estimating God’s ability in me by past experience of what I have been able to do or the past experience of what others have been able to do. I should be basing it on what God says he is able to do in me. I believe “all things” in the above verses are all those things that are in God’s will. If I am correct in this, then the only way “loving God with my all” would be excluded from the verses above would be for it to outside of God’s will for me. In other words, not keeping the greatest commandment would be outside of God’s will for me! Can you clarify your position here using the Bible? What is your definition of “all things” in the above scriptures?
Rom 12: 2 And do not be conformed to this world, but be transformed by the renewing of your mind, so that you may prove what the will of God is, that which is good and acceptable and perfect. NASU