I'm feeling weary even when i havnt done anything!!!?

Yeah this is the problem im facing from the past 6-7 months....I wanna pray early in the morning, i wanna keep myself fit by doing some exercise..but i easily find excuses like my body getting weary and all sorts of things...does God really want me to pray even when i do not get enough time to pray? should i force myself to pray even when my body doesnt agree...will my praise n worship have any significance under these conditions? pls help me in getting through this.