Life is not easy, it is hard.
Through the hard, sad, painful & difficult times of life though, God will not leave you. He knows those times are going to come, and being in His presence does not prevent them from coming, but His presence during those times is the source of strength to push through and endure. If He is that source and we do not rely on our own strength, we will experience a joy even in the midst of the trouble. That joy is called hope.
Then, when we come out on the other side of the struggle, we are stronger because our faith in God will increase. We will feel more ready for the next struggle & go into it stronger because of the increase in our faith.
If, on the other hand, we rely on our own strength, we will begin to see our struggle as futile and lose hope. Once we lose hope we will fight less. When you fight less, the opponent (in this case whatever the trouble is) begins to overcome you.
Even if you succeed in overcoming the struggle on your own, it is an empty victory. You have gained nothing. What have you gained that will help you when the next struggle comes? It will come, and when it does, you may remember the last struggle & feel emboldened that you have the strength to overcome this one as well.
The problem is that when the first struggle is finished and we have overcome, we feel strong for having done so. As time goes on, we brag (even if only to ourselves) that we are strong. We use the experience of the last struggle as proof. Every time we think about it we remember it as the struggle being bigger & our strength stronger than it really was. We are actually “puffing up” our own strength. Therein lies the other problem. Our strength is fake, it is full of hot air with no real substance.
When the problems arise again that strength gets deflated and we start thinking the last victory was just coincidence or luck. At some point in your life, if you depend on your own strength, the confidence & hope gained from other victories, will leave you doubting that you ever had any strength to begin with.
But God, God will never leave you. When you rely on Him for your strength it is easier & infinitely more trustworthy for the next battle than the exaggerated confidence of your own strength.