People do not lack strength they lack will.

Ability is more widely distributed than resolve, which is a claim worth qualifying before it turns into a stick to beat anybody with. Plenty of people genuinely lack time, money, health or safety, and no amount of will covers that. Where the line applies is the narrower case of someone who could and does not, and who has explained it to themselves as inability.

If you suspect you are in that case, stop debating whether you are capable and set the smallest possible first action. Willingness tends to follow motion rather than arriving ahead of it.