Let’s say you are on an outing and carry a small water bottle with very little water. As you travel and keep the bottle with you slowly in the next one or two hours the bottle starts looking like a burden, now let another 2 hours pass, and the bottle will seem like a nuisance and you will most likely drink the water and throw the water bottle away.
Just imagine if a small and helpful water bottle can cause mental tiredness, how much a problem hovering in your mind will tire you.
So don’t keep problems in your mind it will get bigger. It will fester in your mind. Either solve it or ignore it, if can’t ignore it, learn how to unlearn things for ignorance.