No soldier on duty entangles himself in the affairs of life, that he may please him who enrolled him as a soldier.
Here Paul encourages Timothy to constancy and perseverance in his work: Be strong in the grace that is in Christ Jesus, Ti2 2:1. Observe, Those who have work to do for God must stir up themselves to do it, and strengthen themselves for it. Being strong in the grace that is in Christ Jesus may be understood in opposition to the weakness of grace.
Commenting on 2 Timothy 2:1-7
"No one while serving as a soldier." the affairs of (this) life--"the businesses of life" [ALFORD]; mercantile, or other than military. him who hath chosen him--the general who at the first enlisted him as a soldier. Paul himself worked at tent-making (Act 18:3). Therefore what is prohibited here is, not all other save religious occupation, but the becoming entangled, or over-engrossed therewith.
No man that warreth entangleth himself with the affairs of [this] life; that he may please him who hath chosen him to be a soldier. (b) With affairs of household, or other things that belong to other ordinary businesses.