Loving Jesus is the ONLY thing that you can do with ALL your heart, ALL your might, ALL your mind, and ALL your strength. Anything else we love, or anything else we do, we cannot do it with the same level of purity and dedication. We cannot even love sin with all our heart, might, mind, and strength.
The reason for this is because there will always be a part of us that is still tied to the Christ, no matter what else we do.
Our eye cannot be single to anything else, so why not adjust our focus, our aim and place our affection (heart), our faith (might), our loyalty (mind), and our effort (strength) on the one place where it is possible to be single-pointed? He is the only thing worthy of our attention, our time, and our service.
As one protestant man who received his Second Comforter said: I want to serve Him because He deserves to be served.