It is a comforting thought to remember that the Lord draws near to His people in their trials, and blessed be His name, He has promised never to leave nor forsake those who are His. Yet the true comfort of Scripture lies not in the notion that you are strong in yourself, or that you can in your own power conquer all that is before you, but in this, that God Himself is the strength of His people.
The Psalmist declares, For You are the glory of their strength, Psalm 89:17. All strength of every sort comes from God. Even the vigour of youth and the maturity of manhood belong to Him, and how much more that spiritual strength by which a soul endures affliction and overcomes sin. It is impossible that God's true saints should be overcome, not because they are strong, but because they have a glory of strength that nothing can destroy, even the Lord Himself.
You write that God never gives you anything you cannot handle. The Word of God teaches us something more humbling and more hopeful. There are times when there remains no strength in you, nor any ability of any kind or sort, and then you are to fling yourself upon the Divine strength and lay hold upon it. The Lord Himself says, I will strengthen them, Zechariah 10:12, and therefore it will be fitly infused and wisely balanced. The promise of Scripture is not, as your days so shall be your own strength, but that as your days, so shall your strength be, for He gives it.
How then are we to renew our strength. The prophet answers, They that wait upon the Lord shall renew their strength, Isaiah 40:31. To wait upon the Lord is to rely wholly upon the merit of Jesus, to come armed with God's truth and backed by God's Spirit, to seek in prayer what He has promised to give. God's promises are our precepts. What He promises to give, it is our duty to seek. If He promises that we shall renew our strength, let us have the promise fulfilled to our faith.
You also speak of loneliness, and of never being truly alone. Our blessed Saviour knows that sorrow well. He was left alone, alone just when most, as Man, He needed human sympathy, and He said, yet I am not alone, because the Father is with Me, John 16:32. God's people are frequently made lonely through obedience and through trial, but the words of God's Book, made living to you, shall be to your mind as angels, and God Himself shall have fellowship with you. If you lament your loneliness, cure it by seeking heavenly company.
This nearness and this strength belong to those who are indeed God's people through faith in Jesus Christ. By nature we were not God's people, our thoughts contrary to His thoughts, our ways such as He could not endure. But the blood of Jesus Christ, God's dear Son, cleanses us from all sin, and those who trust Him are justified and brought nigh. Apart from Him we have no strength and no abiding presence to claim.
Therefore, do not trust in your own firmness to conquer your challenges. Confess your weakness, and look to Christ who died for the ungodly. Wait upon the Lord continually, plead His promise, and He will be the glory of your strength. In your frailty He will make you strong for His work, strong to suffer, and at last strong to leap out of this frail body into the presence and glory of God.